Masonry Techniques of the Inca’s Master Builders

The Inca civilization is often depicted as being shrouded in mystery, where how they achieved their incredible stonework is treated like an impenetrable enigma. But the Inca Empire, or Tahuantinsuyu, was still dominant throughout South American at the time of the European conquest. It stretched from Colombia down into Chile and Argentina, with a peak population of over ten million people before the arrival of European pathogens. Much of their culture was witnessed and documented by various early Spanish chroniclers in the 1500s.

Over the last decade, I’ve combed through many of these early colonial-period writings. Not only do they detail the Inca’s history and way of life, but to my surprise, they also included many references to their stonemasons’ ingenious building methods. This collection of early Spanish references presents a detailed picture of how their impressive stonework was accomplished.

These historical records were then cross-referenced with other lines of physical evidence, which does support what the Spaniards described. As part of this project, I returned to Peru to gather photographic evidence from over thirty Inca sites. The following collection of photographs illustrates various aspects of their construction techniques, including how the stones were quarried, transported, split, shaped, fitted, and dressed.

This paper also examines a number of what initially appears to be unexplained anomalies, such as a patchwork of masonry styles and seemingly ‘melted’ surfaces. These have fueled a number of “alternative-history” theories surrounding the origin of this stonework. These are, however, resolved with a better understanding of the region’s history and geology. In sum, what follows is one of the most comprehensive and evidence-based accounts of Inca construction techniques ever compiled.

Sections

• Introduction
• What Was Documented by the Spanish Chroniclers?
• Moving the Megaliths
• Quarrying, Cutting, and Shaping
• How Did They Precisely Fit Their Polygonal Stonework?
• The Purpose of the Nubs
• Clearing Up Stone-Melting Confusion
• The Many Problems of the Alternative-History Timeline
• Conclusion: The “Secret” Behind the Incas’ Monumental Architecture
• Sources

What Was Documented by the Spanish Chroniclers?

After the Spanish conquest, the Inca’s skilled stonemasons didn’t suddenly vanish. They continued their craft on post-colonial Spanish buildings and cathedrals, in what researchers call a “Neo-Inca” style (Nair, 2003; Kauffmann Doig, 1965). A few of these Spaniards recorded firsthand accounts. One of the most well-regarded of the chroniclers, Pedro Cieza de León, personally witnessed their masons at work while in Cusco:

“As for laying foundations, making strong buildings, they do this very well; it was they who built the houses and dwellings of the Spaniards, and they made the bricks and tiles, and laid large, heavy stones, putting them together so skillfully that it is hard to see the joinings. They also make statues and other larger things, and in many places it is clear that they have carved them with no other tools than stones and their great wit.”

- Pedro Cieza de León (1518-1554), The Chronicles of Peru (1553)

An example of this transitional-period stonework is seen in the walls of Casa de las Sierpes (House of the Snakes) in Cusco. This building was constructed by Don Pedro Bernardo de Quiroz, following his appointment as attorney general and judge in 1582. He reused pre-existing Inca stones from near the plaza of the convent of Santa Clara. For his lintel, he “commissioned two figures of mermaids with the heads of sea lions, female and male, to be carved for the portal of his house (Amado Gonzales, 2003).” Although not megalithic, this building does demonstrate that precisely-fitted stonework was still being produced here decades after the fall of the Inca.

Spanish chroniclers preserved much of the Inca’s oral history, which spanned back centuries. While the Inca didn’t have a complete written language, they did have wise elders in their society whose primary role was to recall and pass down their history. They converted their stories into songs as mnemonic devices and recounted the deeds of past rulers during important events (Cieza de León, 1554).

The Inca were meticulous record keepers, using their quipu system of knotted strings to record numerical data and some symbolic information. With these records, they tracked tribute payments from their conquered villages (akin to taxes). This included the number of workers that each dedicated to the empire’s monumental construction projects under their “mit’a” system of shared labor (Polo De Ondegardo, 1571; Cieza de León, 1554; Rowe, 1946; Acosta, 1590). Leading these construction efforts were the Inca’s elite class of architects and master stonemasons (Cobo, 1653):

“The Inca kings had a large number of architects and master stonemasons who became highly skilled in their occupation and made their living from it. All of the building that they did was for the king, who always kept them occupied with the many fortresses, temples, and palaces which he had built throughout all of his kingdom... there was no province in all of the Inca's states that was not enhanced with these skillfully made stone structures.”

- Father Bernabé Cobo (1582-1657), History of the New World (1653)

These records trace the rise of the Inca, stretching back to Manco Capac’s founding of the Inca Kingdom in Cusco, through the line of Inca kings to the capture of Atahualpa by Francisco Pizarro. The most notable of these rulers was the great Pachacuti Inca Yupanqui, “Turner of the World”, who is said to have begun the rapid expansion of the Inca Empire. Their history tells of him reconstructing the city of Cusco from its foundations over two decades with 50,000 men:

“He had decided to rebuild the city of Cuzco… Inca Yupanqui outlined the city and had clay models made just as he planned to have it built. … the whole seat of the city was marshes and springs of water. He ordered that all of the springs be canalized in such a way as to be piped to the houses of the city and made into fountains to supply water to the city. At the same time, he ordered others to prepare the foundations of the houses and buildings of the city. … Then Inca Yupanqui ordered everyone from the city of Cuzco to leave their houses, take out everything they had in them, and go to the small towns nearby. As this was done, he ordered those houses to be torn down. With this done, cleaned up, and leveled, the Inca with his own hands, along with the rest of the lords of the city, had a cord brought; indicated and measured with the cord the lots and houses that were to be made and their foundations and structures. With all of this prepared, the foundations were dug. Having brought the necessary equipment, they started to build their city and its houses. While these buildings were being made, the work went on continuously with fifty thousand Indians on the job. From the time that Inca Yupanqui ordered the beginning of the improvements on land and rivers of the city and the construction of buildings until everything you have heard about was completed, twenty years elapsed.”

- Juan de Betanzos (1510-1576), Narrative of the Incas (1576)

Pachacuti Inca Yupanqui is also credited with rebuilding their most sacred Temple of the Sun, Qoricancha, in the same location of a prior temple constructed by Manco Capac (Cieza de León, 1554; Betanzos, 1576). And under his reign, construction began on Sacsayhuaman, the megalithic fortress overlooking the city. Construction on that site continued through reigns of Pachacuti’s son, Topa Inca, and grandson, Huayna Capac:

“From the time of the good King Inca Yupanqui, under whose reign the first material was assembled, until that of Huaina Capac, the Incas worked for over fifty years to erect this fortress; there are even those who say that they never finished it, and they give as proof this "weary stone" which, according to them, was to have been used for further construction, before civil war and the arrival of the Spaniards put an end to all these projects, and to the Inca Empire itself.”

- Garcilaso de la Vega (1539-1616), The Royal Commentaries of the Incas (1609)

“[Pachacuti] Inca Yupanqui was the Inca who started building the fortress of Cuzco, outlining and arranging it, [and] ordering that the foundation [stones] be quarried, the likes of which had never been seen before in Peru. ... “[Tupa Inca Yupanqui] also commanded that the construction of the fortress, which his father, [Pachacuti] Inca Yupanqui, had started be continued with great care, as these famous and renowned buildings would make his name last forever. He [also] ordered the streets and canchas of Cuzco to be straightened, and new buildings be constructed. He also ordered that the royal roads be organized from Cuzco to Chile and to the mountains above Charcas, and below to the coast [all the way to] Quito. So much effort was expended that it was as if he were personally involved in every aspect of the project.”

- Martín de Murúa (1525/1540-1618), The General History of Peru (1616)

How reliable is this historical timeline preserved by the Spanish? Numerous studies have attempted to answer this question by comparing these Spanish works to radiocarbon dating done at numerous Inca sites. The most commonly accepted historical timeline is John Howland Rowe’s interpretation of Cabello Balboa’s chronicle, which was based upon the Inca’s oral history. While stone itself can’t be directly dated, researchers are able to date other organic material used in these buildings’ construction and under foundations, in addition to dating other artifacts. These studies have found that, while mostly accurate, the Inca Empire’s expansion started a few decades earlier than the Rowe/Balboa chronology (Adamska & Michczyński, 2016; Marsh et al., 2017; Ogburn, 2012; Ziółkowski, 2021). This earlier expansion implies that they would have had more time to construct their numerous fortresses, temples, and outposts.

More broadly, these studies do confirm that these sites were indeed constructed by the Inca, not from some earlier civilization from thousands of years prior (a topic we’ll revisit in the final section, examining the “alternative-history” chronology). The construction of these sites wasn’t ancient history for the Inca either. Pachacuti is believed to have died in 1471, whereas Huayna Capac died around 1524, less than a decade before Pizarro captured Atahualpa in 1532. Those Inca descendants telling the Spaniards about this construction at Sacsayhuaman would have likely seen some of it firsthand.

How Were the Megaliths Moved?

One of the greatest engineering challenges faced by the Inca construction was moving the enormous megaliths. The largest stones at Sacsayhuaman are estimated to be 100-200 tons (Šaravanja et al., 2023; Scarre, 1999). How could the Inca, without modern machinery or strong draft animals like horses and oxen, have moved such massive stones from their quarries?

A few of the chroniclers addressed this very question. The solution was the collective strength, ingenuity, and coordinated effort of multitudes of workers. During their construction of Sacsayhuaman, thousands of laborers hauled the megaliths using thick ropes (Cieza de León, 1553):

"He ordered twenty thousand men sent in from the provinces, and that the villages supply them with the necessary food, and if one of them took sick, that another should be sent in his place and he could return to his home. These Indians were not permanently engaged in this work, but only for a limited time, and then others came and they left, so the work did not become onerous. Four thousand of them quarried and cut the stones; six thousand hauled them with great cables of leather and cabuya [fibrous rope]; the others dug the ditch and laid the foundations, while still others cut poles and beams for the timbers... Overseers went around watching what they did, and masters who were highly skilled in their work. Thus, on a hill to the north of the city, at its highest point, slightly more than a bow-shot distance, this fortress was built which the natives called the House of the Sun, and we the Fortress."

- Pedro Cieza de León (1518-1554), The Chronicles of Peru (1553)

Other Spanish chroniclers also mentioned them pulling these stones with ropes:

"They found that there was an abundance of stone and large quarries in the vicinity of Salu. … Immediately after arriving there, they gave the order about how they were to bring and transport the building stones. For this purpose, they had a large number of ropes, thick cables of sinew, and sheep [llama] hide."

- Juan de Betanzos (1510-1576), Narrative of the Incas (1571)

“To this labour was added the conveyance of stones from great distances by force of men’s arms. Any one who has seen their edifices, will not doubt their statements that thirty thousand men were employed.”

- Polo De Ondegardo (1520-1575), Narrative of the Rites and Laws of the Incas (1571)

Some Andean cultures still make exceptionally strong traditional rope using various materials. While visiting a Kichwa community in Ecuador (who speak a dialect of the Inca’s Quechua), two women demonstrated how they made rope from a succulent called Furcraea cabuya (mentioned in one Cieza de León translation). Just a few thin strands wound together were already too strong for someone to break.

Another enduring example of traditional rope making can still be seen at Q’eswachaka. Every year a Quechua community joins together to reconstruct a traditional Inca bridge. The collective effort likely resembles how Inca era workers once joined together to haul stones. The festival takes place over four days, where first the women weave the ropes out of ichu grass, which is widespread throughout the highlands. Dozens of men then haul the heavy thick ropes across the canyon to re-erect the bridge. Rope made from llama leather was then used for cross-support bands.

A 1996 engineering study tested the strength of the ichu grass ropes (Ochsendorf). Each could support at least five thousand pounds when two inches thick. When braided into thicker cables, they were estimated to hold 50,000 pounds. That strength was crucial, as Inca rope bridges once carried long caravans of llamas ladened with goods.

When calculating the force required to move megaliths, one point that’s often missed is that their entire weight would not have been lifted. Rather, to move them horizontally, workers only needed to overcome friction and generate enough lateral momentum. On an incline, only a fraction of the stones’ total weight added to the pulling force required. This leads to the Inca’s extensive use of earthen ramps and other friction-reducing methods.

Father Bernabé Cobo, a Jesuit missionary, witnessed their use of ramps in Cusco:

“The stones were taken to the work site by dragging them, and since they had no cranes, wheels, or apparatus for lifting them, they made a ramp of earth next to the construction site, and they rolled the stones up the ramp. As the structure went up higher, they kept building up the ramp to the same height. I saw this method used for the Cathedral of Cuzco which is under construction. Since the laborers who work on this job are Indians, the Spanish masons and architects let them use their own methods of doing the work, and in order to raise up the stones, they made the ramps mentioned above, piling earth next to the wall until the ramp was high as the wall.”

- Father Bernabé Cobo (1582-1657), History of the New World (1653)

Several ramps remain visible today at Inca quarries and archeological sites, such as these Chullpas (funerary towers) near Puno. A sign at Sillustani mentions that one of the ramps still had a couple large stones left upon it leading to a Chullpa that was still under construction. At Cutimbo, a ramp extends toward the edge of cliff, presumably to haul the loose stones up from the lower quarry. And at other quarries, ramps can be seen leading to individual megaliths that were in the process of being hauled out (Protzen, 1985; Protzen & Nair, 2013).

In some areas, quarries were located near construction sites, so stones didn’t need to be moved particularly far. At Machu Picchu, some alternative-history tour guides give the false impression that stones were moved from the valley thousands of feet below, while ignoring an upper quarry next to the Temple of the Three Windows. Similarly, two quarries exist nearby and uphill from Sacsayhuaman, and large stones are scattered across the landscape around there.

Other stones were indeed transported from distant quarries. Much of the stone from Cusco was sourced from the Rumicolca quarry, 18 miles (30 km) away. Although distant, this was through a relatively flat river valley, along their sprawling road network (the Collasuysu branch of the Qhapaq Ñan). It would have generally been smaller stones that were transported this distance. The stone used in Cusco’s pre-colonial stonework averaged roughly 100lbs, with some of the larger stones at Qoricancha only being around 300lbs (Sacred Geometry Decoded, 2022).

While there is also an upper quarry at Ollantaytambo, a primary source of its stone was a hillside across the river valley at the Kachi Qhata / Cachiccata quarry. Hauling megaliths through this valley is undeniably an impressive feat. To accomplish this, the native workers built a well-engineered road, leading down from the quarry and then directly up to the megalithic zone of Ollantaytambo. Those trying to exaggerate the sense of mystery surrounding this site tend to ignore the existence of this gigantic ramp, as it undermines their “lost advanced technology” narrative. This ramp leads up the side of the mountain at a gradual eight-degree incline, and is 4-8m wide, enough for a few columns of men pulling with ropes (NOVA, 1996; Protzen, 1993; Miano, 2021).

Along this route from the quarry there are numerous “piedras cansadas” (tired stones) that have been abandoned while in transit, with one resting at the base of the ramp. These provide further insights into their transportation methods. An excavation under one of these megaliths revealed how they constructed roadbeds to help move these massive stones (Protzen & Nair, 2013). This carefully prepared surface contained multiple layers of soil, gravel, and clay. This surface would have lowered friction and reduced the likelihood of stones catching on other rocks. Soil was pushed up along the leading front-edge of this stone, as evidence of it being dragged. Drag marks can also be seen on some large stones.

Decades earlier, another megalith near Ollantaytambo revealed a different friction reducing technique: “Sr Luis Llanos informs me that a treasure hunter at Ollantaytambo dug under a large Inca block abandoned between the quarry and the site and found remains of wooden rollers (Rowe, 1946).” Softball-sized spherical stones found at some sites are also thought to have been used as rollers. Additionally, numerous bronze pry bars have been found at Inca sites, which could apply leverage in helping to shift and re-position stones (a technique still used today by Peruvian stone masons).

In 1996, a NOVA documentary successfully replicated this manual method of hauling megaliths, confirming that the tired stones could be hauled by a coordinated team pulling with ropes. They gathered 250 men, women and children from around the village of Ollantaytambo to move a 15-ton block up an incline approximating the large ramp leading to the Sun Temple. Although the stone was initially a challenge to raise from the hole where it sat, once it became dislodged, they were able to maintain a relatively fast momentum.

This same method can be scaled up to more men (and excluding women and children), with more ropes, pulling even larger stones. An example of what this may have looked like can be seen in the Nias people from Indonesia, who similarly moved megaliths with ropes until about the 1950s. Although the size of the Inca megaliths is remarkable, numerous other examples across the world and throughout history have shown that larger stones can be moved by manpower alone.

How Were the Stones Quarried, Cut, and Shaped?

The Inca-era masons crafted some of the finest stone monuments in human history. In their worldview, the natural world was permeated with consciousness. Rock to them held a sacred and spiritual significance. Their mythology even spoke of humanity as being born from stone. This reverence is reflected in the painstaking care and precision of their interlocking masonry, shaped through countless hours of work. Their creations sought a harmonious balance with the landscape, with passageways and court yards opening to dramatically framed vistas. Other structures appear to emerge out of the bedrock, with bricks closely hugging the curves of natural outcroppings.

How was their remarkable masonry accomplished? Modern masons have become accustomed to working with strong steel chisels, diamond-tipped saws, and high-speed grinders. Few today are aware of how this work was done in the centuries before the advent of these tools. For those looking for some lost technology, the answers presented here may not be particularly satisfying - it had more to do with their process and techniques than it did with any advanced tools.

The ingenuity of Inca-era masons is evident in the tool marks that show how they split rocks apart. They carved a line of grooves and hammered in wedges to split the stone cleanly in two. This same technique is still used by some modern quarry workers. They may have also used an ancient Roman-style variation, pounding in wooden wedges later soaked with water to expand and split the rock. Rocks with rows of chiseled out holes can be found at numerous Inca sites, including Machu Picchu’s quarry, a tired stone at Ollantaytambo, Tipón, and on stones in Cusco. While this stone splitting technique appears to be relatively common, other times they would have just selected from loose rocks that scattered the landscape, or by prying them out of bedrock along pre-existing fractures (Protzen, 1985).

Another stone with a long thin cut at Ollantaytambo has led some to suspect that these masons must have had some kind of drag saw or circular saw. However, the groove is wobbly, not straight, so couldn’t have been made with a saw blade. Upon closer inspection, you can see crystals inside of the crack, revealing that this was simply a calcite or quartz vein. Those minerals have since mostly dissolved, leaving behind the misleading appearance of a thin saw cut.

Some mistakenly assume that this stone at Ollantaytambo shows saw cut marks, but closer examination reveals that these are natural cracks filled with mineral deposits, not tool marks.

After splitting rocks to their rough size, their masons used hammerstones for further shaping. The use of these hammerstones is described in various Spanish accounts (Cieza de León, 1554; Polo de Ondegardo, 1571; Father Bernabé Cobo, 1653; Garcilaso de la Vega, 1609; Murúa, 1616).

“The implements that they had to cut the stones and work them were hard, black cobblestones from the rivers, with which they worked more by pounding than cutting.”

- Father Bernabé Cobo (1582-1657), History of the New World (1653)

“This work was very toilsome, for all their buildings were of masonry, and they had no tools of iron or steel, either to hew the stones out of the quarries or to shape them afterwards. All this was done with other stones, which was a labour of extreme difficulty. They did not use lime and sand, but adjusted one stone to another with such precision that the point of junction is scarcely visible.”

- Polo De Ondegardo (1520-1575), Narrative of the Rites and Laws of the Incas (1571)

“They had no other tools to work the stones than some black stones hihuana with which they dress the stone by pounding rather than cutting.”

- Garcilaso de la Vega (1539-1616), The Royal Commentaries of the Incas (1609)

Beyond these Spanish accounts, two types of physical evidence confirm that hammerstones were the primarily tool used. First is the prevalence of hammerstones found at both their quarries and construction sites. Hiram Bingham’s team found hundreds of these hammerstones during his excavations of Machu Picchu (1952). Some had depressions for the thumb and finger to help with grip. These stones had been selected for their toughness (resistance to cracking), and included cobblestones, dolerite, quartzite, olivine basalt, or hematite, which naturally contains iron (Bingham, 1952; Protzen, 1985; Rowe, 1946). The hematite or basalt hammers are probably the “black stones” that Garcilaso de la Vega called hihuana (1609). At the Rumicolca quarry, Jean Pierre Protzen found 68 river cobblestone hammerstones amongst the fractured andesite, of a variety of stone that he notes were easily determined to be foreign to the site (1985).

The second type of physical evidence that confirms the use of hammerstones are the impact marks seen on these stone faces. These are especially visible on the limestone blocks used at Sacsayhuaman and neighboring sites. This calcium-carbonate rich material metamorphizes into white dots when struck (Rowe, 1946; Protzen, 1985). Notable too are the larger hammerstone impact marks on their front-facing surfaces versus smaller dots on the beveled edges where they shifted to a smaller tool for the detailed work. When you look closely at this limestone, you can even see some jagged angular lines where flakes chipped off. During the Chincana Project’s excavations at the base of those walls, there was a layer of small angular gravel chips in the soil, which would be consistent with them flaking off material (Adams, 2025). While less noticeable, similar hammerstone tool marks can even be seen on granite and andesite blocks. And yes, these marks are also seen on even the precise-fitting, polygonal megalithic stonework.

Some readers may question the feasibility of using these simple hammerstones. However, humans have a long history in skillfully working stone in this manner. Over twelve-thousand years ago, Paleolithic hunters in the Americas were crafting finely-made, bi-faced spear points out of hard varieties such as flint, quartzite, obsidian, and jasper. By just using simple hammerstones, struck at the correct angle, they were able to quickly chip away flakes of material into sharp, symmetrical blades.

The techniques used by the Incas’ workers weren’t too dissimilar to these Paleolithic knappers. Stones like granite, andesite, and rhyolite, commonly used in their buildings, can similarly be chipped away using the right technique. In his experiments, Jean Pierre Protzen observed that striking the rock at an angle of 15-25 degrees, and rotating the hammerstone at the moment of impact, increased the amount of flaking. This relates to a common misperception about the Mohs hardness scale, which some use to argue for the seeming impossibility of using simple hand tools on harder varieties of stone. But this scale only ranks how easily each will scratch, not how easily it will crack or flake. In the words of John Howland Rowe, “the process of working stones with stone hammers is not as slow and laborious as many people who have never tried it are inclined to believe (1946).”

While hammerstones were the primary tool used in the final shaping and dressing, chisels were required for carving out sharp inner corners. Most commonly, they likely used shards of sharp rocks as chisels. Any loose shards of the same material or harder would serve this purpose. During their study of Tiwanaku, Stella Nair used obsidian shards to replicate carving out sharp 90-degree inner corners within Rhyolite, a high-silica volcanic rock with similar hardness as granite or andesite (2013).

Although Inca sites don’t appear to have inner corners as tight as at Puma Punku, they did frequently carve out flat religious offering platforms on their “huacas” (sacred places of worship). These intentionally carved altars are often mistaken for quarries by those who aren’t familiar with Inca religious practices. The Spanish chroniclers note that roughly four hundred of these huaca sites were established at key points along their road network, which they used to venerate their various ancestors, oracles, and deities (Cobo, 1653; Polo De Ondegardo, 1571; Ayala, 1613).

The Inca were also skilled in metallurgy and created bronze chisels for this work. While raw copper is a relatively soft metal, the local variety also naturally contained arsenic, which was mixed with tin and silver. This created a durable bronze that was two to four times harder. They then cold-hammered this metal, increasing the hardness by another four times. The end result was that these “Arsenical copper and bronze tools were of sufficient hardness and substituted for iron (Peterson & Brooks, 2010).”

How Did They Precisely Fit Their Polygonal Stonework?

While the prior questions of how these rocks were quarried, moved, and shaped is no longer a mystery, how exactly they fitted such precise masonry still needs to be addressed. Rather than invoking some lost technology, this final step is better framed as a matter of lost methods or techniques. Once again, Spanish accounts and remaining physical evidence do provide revealing clues as to how this was done.

As a quick tangent, it's worth noting that the Incas’ architects used a range of styles depending upon the varieties of stone available and the type of structure. Not all Inca structures used the tightly-fitted masonry for which they’re renowned. In the coastal deserts, where earthquakes were less of a concern and quality rock wasn’t as readily available, they commonly built with adobe, such as at Acllawasi, Tambo Colorado, and Huaca la Palma. Even around Cusco, adobe and rough rubble masonry were common on less significant buildings.

The finest stonework was reserved for the higher status buildings, such as temples, fortresses, and palaces. Here we commonly see two main masonry styles: ashlar, which uses four-sided rectangular blocks, and polygonal, which can have various irregular angles. Their ashlar masonry was typically coursed, meaning that each row of stones is flattened on top, so that subsequent rows are laid upon a relatively flat surface. The joints of this style are simpler than in polygonal masonry. Because the stones join along straight edges, only the joint angle needs to be correct for a precise fit. However, to shape irregular rocks into the rectangles of ashlar masonry requires that more material be removed.

Polygonal masonry, in contrast, allowed builders to take advantage of the wide variety of shapes and sizes of rock that are available to them. With this style, they could instead carefully select stones best suited to filling each gap, as if they were playing a game of Tetris. They then only needed to incrementally shape the edges to make a tight fit. So, while polygonal masonry may initially look more complicated, this style would generally have been less time consuming for them than ashlar, since the final stone shapes were closer to that of the original rocks. Their polygonal masonry also offered superior earthquake resistance because of its tightly interlocking design.

When looking at the tightly-mated joins between these stones, many assume that the precise fit continues beyond their outer faces to the internal joins, but typically only the faces of rising joints have this tight fit. Internally, they are often slightly wedge shaped, angling inwards and leaving gaps inside between adjoining blocks. These gaps were packed with a sticky red clay (llàncac allpa) and rubble (Cobo, 1653; Protzen, 1985).

“The Indians did not use mortar in these buildings, that all of them were made of dry stone; the first reason for this is that they did not use lime and sand for construction (never having discovered this type of mortar), and the second reason is because they set the stones together with nothing between them on the exterior face of the structure. But this doesn’t mean that the stones were not joined together on the inside with some type of mortar; in fact it was used to fill up space and make the stones fit. What they put in the empty space was a certain type of sticky red clay that they called llanca, which is quite abundant in the whole Cusco region.”

- Father Bernabé Cobo (1582-1657), History of the New World (1653)

By mating only the faces of rising joints, the masons significantly reduced the time and effort required. In certain high-status buildings, they took the additional effort to align adjoining stones within the walls as well. At Qoricancha they did this with an interlocking, jigsaw-like pattern for better earthquake resistance. Bedding joints also required closer fits internally for better stability. Concaved imprints were often carved into lower rows to securely seat the above stones.

The question remains, how did they fit these stones together so perfectly? Additional clues can be found at Machu Picchu, where it appears as though the stonework around the Temple of the Three Windows was never fully completed. This work may have been abandoned while in progress due to the Inca civil war or the Spanish conquest. A number of rocks here are still in the process of being fitted and dressed. Two large stones are still tilted slightly back with smaller rocks wedged underneath. Their lower edges are in the process of being shaped to fit with the lower rocks, as explained by Fernando Astete (chief supervisor of Machu Picchu), in the documentary “Ancient Superstructures: The Secrets of Machu Picchu” (Kissous, 2020).

According to some of the Spanish chroniclers, an essential part of this process was simply perseverance, where they did repeatedly need to re-check their joints until a tight fit was made:

"If we consider the number of times they must have fitted and taken off one stone before this accuracy was attained, an idea may be formed of the toil and of the number of workmen that was required."

- Polo De Ondegardo (1520-1575), Narrative of the Rites and Laws of the Incas (1571)

“All this was done through the power of many people, and with great suffering in the work: because in order to fit one stone with another, as they are so well adjusted, it was necessary to try the fit many times, since most of them were neither even nor full.”

- José de Acosta (1540-1600), The Natural and Moral History of the Indies (1590)

“This work certainly is very hard and tedious. In order to fit the stones together, it was necessary to put them in place and remove them many times to check them, and since the stones are very big, as we see, it is easy to understand what a lot of people and suffering were required.”

- Father Bernabé Cobo (1582-1657), History of the New World (1653)

There are a few techniques that they may have used to make this process simpler, requiring fewer movements of the stones. They could have also used their sticky red clay to create imprints when testing the joints, to show where additional material needed to be removed (Sacred Geometry Decoded, 2017). A similar method uses stone dust or sand to leave impressions while creating bedding joints. During his research at Ollantaytambo, Jean Pierre Protzen used this technique with only hammerstones to tightly fit a block to a bedding joint (NOVA, 1996). The entire process took him a few hours.

Although this may initially seem time consuming by modern standards, it was feasible given the tens of thousands of laborers who worked over decades on these monuments. For efficiency, the largest megaliths would be placed first and then remain seated while the smaller stones would then move in to be fitted with them. Despite the fixation on the largest stones, the vast majority of their stones were small to medium sized and could have been easily fitted by small teams of workers (see Sillustani workers photo above).

Another hypothesis, proposed by Vince Lee, is that they used a scribe technique to first match edges of closely positioned neighboring stones (Lee, 1986; Miano, 2021). He noticed that carpenters doing log home construction similarly used scribes, allowing them to only move logs once for the final placement. Those skilled in this method would commonly get a tight fit on their first attempt.

With the stones placed next to each other, the scribe would travel along the edges of one stone to check for a consistent spacing with its neighbor, removing material as necessary. In doing so, the two separated stones could be carved to fit, and then ideally moved together in one final movement. Using a technique like this would have saved a lot of effort in fitting some of the larger rocks.

A key element of this scribing method was the plumb-bob, which are small weights hanging from a string, used to find “true vertical” during construction. John Howland Rowe noted that “the Inca know and used the plumb-bob, for which there is a Quechua name (WIPAYCI) in Gonzalez’s dictionary of 1608. Two specimens are illustrated by Bingham (1930), and I picked up a small stone one in the ruins at Ollantaytambo (1946).” The hanging plumb-bob would ensure that the scribe maintained a consistent angle and distance throughout the process.

The Purpose of the Nubs

There’s much speculation surrounding the protrusions on these stones, often called “nubs.” These are commonly suggested to be lifting bosses (Rowe, 1946; Lee, 1986; Protzen, 1985). Others question if they were used for astrological purposes, whether they’re remnants of where liquified stone was poured into molds, or if they hold hidden messages from an undeciphered stone-nub language. While there are a few variations, a close analysis of these protrusions does reveal their true purpose.

Initial clues can be gathered by examining their placement. They tend to be located towards the lower edges of stones, often with only a single, centered nub for narrow stones, and with a pair of nubs on wider stones, one in each lower corner. While common on medium or larger stones, they are rarely found on the very bottom layer of stones that didn’t need to be placed upon other stones.

Many stones show traces of where the nubs were previously located. This can be seen on the south side of Hatunrumiyoc, in Cusco. Here a wall has been crudely dressed in what appears to be rushed or unfinished work, and some of these nubs haven’t yet been completely removed. Another stone at Machu Picchu is in the final process of being dressed. On its bottom right, where a nub would conventionally be located, the nub is now missing where the face is being flattened to match neighboring stones, whereas the bottom left appears to be in the process of being chipped away. The removal of these protrusions after fitting indicates that they had an initial function relating to construction, rather than a purely aesthetic or astrological role.

Another common idea is that these may have been useful in the transportation of stones. However, they are almost always on only one side of the stone, whereas their backs are rough and unworked when used as retaining walls. Because of this, and since ropes would slip off the relatively rounded nubs, this suggests that they were not used to help secure ropes to aid in hauling stones. They are also not found on the tired stones left in transit leading from quarries.

All of these observations are consistent with these nubs being utilized as lifting bosses, used to push the front-edge of stones upwards during the fitting process. Picture what this work would have entailed for masons trying to get a tight fit. If they placed a stone onto a lower row of blocks, but the joint wasn’t quite right, they would have needed a way to tilt the heavy stone back up again. Trying to jam one of their pry bars into the crack would have damaged stones’ carefully shaped edges.

Creating lifting bosses to push up upon is the obvious solution to this problem. For balance, the logical placement of lifting bosses would be exactly where they are found, either with two positioned towards the corners, or one in the center. This also explains why these lifting bosses aren’t as common on smaller stones, since those would have been easier to lift back up again without needing these extra protrusions. It’s little wonder why stone masons in other parts of the world arrived at the same conclusion, adding nubs to their own stones to serve a similar purpose.

"Protuberances were often left on the blocks of stone to provide a purchase for the pry bars, and, in many walls, the protuberances were never removed. They were probably considered decorative, as similar ones were in Greece in the 4th century B. C. The protuberances are usually near the bases of the blocks. … Many stones at Sacsahuaman have indentations instead of protuberances at the base, no doubt for the same purpose."

- John Howland Rowe, Inca Culture at the Time of the Spanish Conquest (1946)

Further confirmation of their function comes from their shape and wear patterns. These nubs aren’t perfectly symmetrical above and below. Rather, their tops are commonly more rounded whereas their undersides have more abrupt edges, sometimes slightly cupped. This would have both reinforced the protrusion from above while providing a more supportive overhang. It also would have allowed workers to push upwards with logs, temporarily propping it back. For those questioning the strength of wood, a 12” diameter log will support in excess of 50 tons (Lee, 1986).

When examining the undersides of these lifting bosses, damage that appears to originate from below is often seen. These chipped or broken nubs are apparent on about half of those remaining nubs at Hatunrumiyoc. Marks such as these would be expected if they were indeed levering upon these with pry bars.

If they could get a tight fit on the first attempt, then there wouldn’t have been as much need for these nubs to re-lift the stones for further shaping. The degree of damage to some of them also suggests that they had been used repeatedly to lift the stones. This is consistent with the multiple Spanish references saying that they needed to re-work and re-fit each stone until a tight fit was made.

While these lifting bosses are the most common form of stone protrusion, there are other varieties that served different functions. The upper edges of walls sometimes have a series of stone pegs extending about a foot. These were used to tie ropes securing their thatch roofs (Bingham, 1952). A few modern replicas roofs have been re-created at Machu Picchu. Another style of protrusion are the diagonal stone steps, which they used for ascending agricultural terraces and walls.

A more enigmatic style of nub can be seen at what appears to be a huaca at Ollantaytambo. These are slightly inclined, and are carved directly into the bedrock, so clearly wouldn’t have been used as lifting bosses or tie downs for roofs. Hiram Bingham noted that stone pegs were also found inside of their homes, which he speculated were for hanging various items including jars of chicha (corn alcohol). If this is a huaca, a religious altar, then they would have made sacrificial offerings of things they valued, a practice that continues today during Pachamama (Mother Earth) celebrations. So perhaps these were used to hang offerings, such as corn, quinoa, and vases of chicha?

“Stone pegs were usually placed between the niches and on a level with the lintels. They made handy hooks for all sorts of purposes. It is quite possible that from them were hung the characteristic water or chicha (beer) jars which had pointed bottoms. Their handles are so placed in the line of the center of gravity as to make it easy to suspend them and, by using a nubbin on the shoulder of the jar, to pour out a drink without having to take the jar down from the peg. The pegs were also convenient for fastening one end of a hand loom, while the weaver sat on the ground with the other end of the loom tied to his or her waist.”

- Hiram Bingham, Lost City of the Incas (1952)

Another possibility is that some of these protrusions also had an astronomical function, as other Inca sites were certainly constructed with those alignments in mind. During the solstice, shadows from the right two pegs are said to cast down into two notches on the ridge of the stone below (Salazar & Salazar, 1996). This doesn’t, however, explain why they are inclined, or the role of the first peg, which doesn’t have a lower notch. It’s also possible too that some of these nubs had dual purposes. For example, while lifting bosses were primarily used to aid in construction, some may have been intentionally left in order to track solar positions during the turning of the seasons. Incan astronomy books claim to have discovered some of these alignments. Skepticism here is appropriate considering that seasonal shadows wouldn’t explain all the unremoved nubs, and occasional solar alignments on a subset of these may be coincidental rather than intentional. Or some of these may have simply been aesthetic, where they enjoyed how their shadows travel across the stone walls as the sun moved across the sky.

Clearing Up Stone-Melting Confusion

As detailed above, we have multiple lines of evidence indicating that the Incas’ stone masons used hammerstones to skillfully shape these stones. That is supported by eye-witness accounts of the early Spanish chroniclers, dozens of hammerstones found at these sites, rock chips found below the walls, and the hammerstone impact marks seen on the rocks themselves.

Despite this evidence, later folklore suggests the Incas possessed plants or acids capable of softening stone. According to this hypothesis, that would hypothetically make it easier to ‘squish’ a stone’s placement into neighboring stones, allowing for ultra tight joints. Jason Colavito recently did a deep dive into the history of this legend (2025). Hiram Bingham was the earliest to mention local folklore of the Incas’ masons using some kind of stone softening liquid:

“The modern Peruvians are very fond of speculating as to the method which the Incas employed to make their stones fit so perfectly. One of the favorite stories is that the Incas knew of a plant whose juices rendered the surface of a block so soft that the marvelous fitting was accomplished by rubbing the stones together for a few moments with this magical plant juice!"

- Hiram Bingham, Across South America (1911)

However, this reference is dated to nearly four centuries after the Spanish conquest, so can it be trusted? The original source of these stories may be related to a much earlier story dating to 1638 about a woodpecker using some kind of herb to dissolve stone, where it was said that prisoners used that same herb to dissolve iron to break out of their chains. But a very similar folktale appeared in earlier classical sources too, so the story may have been brought to the Americas by the Spanish (Froemming, 2006).

A 2017 paper by Helmet Tributsch theorizes that they used an acidic mud to soften the stone. In it, he quotes Cieza de León mentioning "melted gold" being used in place of mortar, suggesting that excerpt is evidence for his proposed acidic stone softening liquid. But rather than this being evidence for stone softening, it might be better understood as referring to the T and O shaped clamps that they used to join their stones together at a few of these sites, including Ollantaytambo and Qoricancha. Molten metal was poured directly into these carved recesses to help lock them in place. The melted gold here may have simply been bronze, which is known to have been used on these clamps.

“Moreover, it is said with certainty that in these buildings of Tambo — or in others that bore the same name, for this was not the only place called Tambo—there was found in a certain part of the royal palace or the Temple of the Sun some melted gold used in place of mortar, which, together with the bitumen they applied, caused the stones to be set and joined firmly one to another.”

- Pedro Cieza de León (1518-1554), The Chronicles of Peru (1553)

There are also some stones at these sites that are alleged to show physical evidence of stone-softening. Rocks appear to have a glassy surface, while others appear almost to be melted. These features can be well explained with a better understanding of the area’s geology.

Limestone, common around Cusco and especially at Sacsayhuaman, is primarily calcium carbonate (CaCO₃), which dissolves in acidic water. This process formed the area’s karst landscape of caves and irregular formations. Industrial-era sulfur pollution has accelerated limestone dissolution. Within just the last century many limestone statues and gargoyles on cathedrals in Europe have had their faces and details erased from acidic rain. This same process has been dissolving the limestone at Inca sites too.

As mineral-rich water drips over limestone, it leaves calcite encrustations similar to stalactites and stalagmites forming within limestone caves. This same reddish calcite is commonly found on raw, uncut limestone in this area, demonstrating that it’s part of a natural process. It is also what gives some of this Inca limestone stonework a glassy-like appearance. Water seeping through joints and along beveled edges deposits more calcite, visible under ultraviolet light as blue fluorescence, while the reddish hue likely comes from iron oxide (rust).

Since this calcite is almost entirely CaCO₃, it dissolves much faster than the surrounding limestone. Areas where there were once calcite filled pockets may have disappeared completely. This explains the snake-shaped hole at Sacsayhuaman, where you can still see a few small chunks of the remaining reddish calcite clinging inside that cavity.

Limestone was only one of the varieties of rock used at Sacsayhuaman. Other sites were constructed with other types, such as granite, rhyolite, and andesite at Machu Picchu, Ollantaytambo, and Tarawasi. And sure enough, this glossy calcite glaze is missing from the stones at those latter sites. This should rule out the theory of that being a primary part of their general stone shaping process.

In some cases, the reddish clay used to pack the interior joints can be seen seeping out through the cracks. The Spanish wrote about observing this technique. As mentioned previously, the inca masons commonly did that so that so they’d only have to join the faces of the stones. And those stones being tightly joined only on their faces is another argument against the stone softening theory. If they were softened, you’d expect their joints to squish into each other deeper into the wall, not just their outer faces.

As shown in the sections above, hammerstone impact marks can sometimes be seen around the edges of these stones, as with their faces too. That work wouldn’t have been required if the stones were somehow softened and squished together. Since those beveled edges were often worked with a smaller tool, they are also sometimes more reflective than the rougher faces, done with a larger hammerstones. This adds to the misperception that these edges have been melted or softened.

Another source of a “melted” appearance is the pattern of hammerstone track lines, shallow ridges and depressions created during final dressing (Protzen, 1985). Masons typically hammered vertically, a natural motion that also avoided collisions with nearby workers. Then once those ridges between the track lines grew those could also be bashed off more easily.

A more extreme version of this stone softening hypothesis claims that these stones were somehow liquefied into a geopolymer, something more akin to concrete, and then poured into molds. Archeologists generally aren’t opposed to the notion of ancient cultures using concrete. It was used extensively by the Ancient Romans. The Maya also created a hardening mortar from limestone, similar in function to concrete. But there is no evidence of concrete from the pre-colonial Andes.

The geopolymer hypothesis also makes little sense in light of the other evidence. Why quarry and haul massive megaliths, as seen with the “Tired Stones” along those routes, if liquid stones could be mixed and cast on site? Why are only exterior front faces of retaining walls smoothed and beveled, while their backs remain rough? Why create irregular polygonal stones instead of standardized molds? Wouldn’t the time involved in making molds have been as equally burdensome as shaping the stones directly? What material used to create molds could have contained tons of liquified rock without rupturing? And where are the molds themselves? With a little intellectual prodding, the full geopolymer idea becomes increasingly implausible.

I imagine that some of the later Spanish colonists, who didn’t get the chance to observe the original masons working with hammerstones, struggled to understand how their superb stonework was done. They too were likely also perplexed about the seeping red clay and calcite glaze. From a layman’s perspective, the polygonal masonry does appear as though the stones have been squished together, so it makes sense why rumors of stone softening spread, becoming folklore. But the stone softening hypothesis doesn’t stand up to closer scrutiny.

The Many Problems of the Alternative-History Timeline

Despite extensive records of Inca oral history, examples of precise post-colonial construction, and radiocarbon dating studies that support an Incan chronology, there is a growing pop-culture alternative-history narrative that the Inca didn’t build these sites. The reasoning behind this counter-narrative is largely based upon the layering of stonework, where some walls exhibit poorer quality towards the top. Some then surmise that only the upper stonework is from the Inca, and the lower, better-quality stonework is from some lost, advanced, globe-spanning civilization, often suggested to be tied to Atlantis.

This claim is frequently made at Sacsayhuaman, where some rougher upper sections of stonework are indeed lower quality. What this narrative gets wrong is that the upper stonework is actually modern re-construction. These are retaining walls that were added to prevent erosion after the site became a tourist destination. Early 1900s photographs show no such walls, confirming they postdate the Inca era. Some even bear modern construction dates chiseled into the stone.

Most tourists are also unaware of the extent of reconstruction at Machu Picchu. When Hiram Bingham first photographed the site in 1911 it was heavily damaged. In the 1950s, many collapsed walls were quickly rebuilt for a Hollywood movie called Secret of the Incas, using much poorer-quality masonry atop the original stonework. Restoration has continued in the decades since, although new stonework is now often marked with reference numbers and scribed lines to track reconstruction. The newer stones also lacks the lichen growth found on older walls (except where older collapsed stones have been repurposed). Keep this in mind when viewing the coarser upper stonework at Machu Picchu.

Numerous other Inca archeological sites have undergone extensive restoration. Visitors often see crews repairing walls. Some of the stonework even faithfully replicates the precision of the pre-colonial masons. At Tarawasi, a few of the tight-fitting upper stones are modern, displaying the year of the repair work (July 2000).

Around Cusco, too, construction continued in the centuries following the Spanish conquest. They intentionally dismantled indigenous temples and palaces in an attempt to erase Inca culture, and to establish their own legitimacy as the new rulers over the region. The Spaniards sourced stones for their cathedrals and homes from existing Inca structures, while building upon the foundations of others. Smaller stones were easier to repurpose for their own construction, whereas megalithic stones, more difficult to transport, were often left behind. In the decades that followed, some pre-colonial buildings that had been partially demolished were then repaired and reoccupied, leading to a blending of Inca and colonial architectural styles.

Cusco has experienced several major earthquakes, including 1650, 1950, and 1986 causing significant damage. Native stories tell of earlier tremors. While Inca architecture was designed to resist these forces, not all the original walls survived these quakes. Considering this seismic history, it’s unsurprising that the region’s stonework varies in quality if rapid repairs were needed following these events.

Pre-colonial Inca stonework also varied in precision. Their master masons and architects focused their efforts on important structures like temples and entranceways. Meanwhile, villagers conscripted from across their empire had differing skill levels in working stone. Rotating work teams naturally produced variations in style and quality.

As a consequence of these factors, many walls have an almost schizophrenic quality to them. Yet while alternative-history influencers often point to instances where rougher stonework sits atop more precise stonework, which they believe supports their chronology, they ignore the many other examples of the opposite, with looser masonry below. These counterexamples further demonstrate that higher precision stonework is not necessarily older.

Another example that contradicts this alternative-history narrative is Rumicolca. This site was originally constructed by the earlier Wari culture (600 to 1000 CE), as an aqueduct supplying water to their nearby city of Pikallacta (Bauer & Hardy, 2022). Most of the stonework on this wall is the same rubble-masonry style found on those other neighboring Wari-era buildings (with some upper sections of the aqueduct being modern reconstruction).

Centuries later, the Inca transformed this ancient aqueduct into a massive gateway for travelers entering Cusco via the main Inca southern road, Collasuyu. They opened two entrances in the wall and reinforced those edges with their more precise fitting masonry. The sequence here should be obvious: it would make no sense for that higher quality stonework to predate the aqueduct since it wraps and reinforces the older Wari wall. And if those refined edges were older, then the Wari would have needed to fill the gaps to allow water to flow across them.

We can also examine the distribution of sites with this architectural style as further confirmation that the Inca were their creators. Apart from the tight-fitting masonry work, buildings attributed to the Inca commonly have distinctive trapezoidal windows, niches, and doors. The narrower upper width likely helped prevent lintel stones from cracking. Their primary entranceways were often double-jambed, with a wider outer frame and a narrower recessed opening.

Iconic Inca trapezoidal, double-jambed doorways, as seen at Vilcashuaman, Machu Picchu, Ollantaytambo, and Winay Wayna.

South American pre-conquest masonry of this style exists only within the boundaries of the Inca Empire. And it is most concentrated around Cusco, the heart of Tahuantinsuyu, at the center of the Qhapaq Ñan road network. This is where the Kingdom of Cusco first began under Manco Cápac around 1200 CE. Numerous examples of these sites are then found throughout the Sacred Valley, along the Antisuyu road leading to Machu Picchu. Inca oral history, as recorded by the Spanish Chroniclers, details of the conquest of that region (Cieza de León, 1554; Betanzos, 1576; Murúa, 1616; Cobo, 1653).

These Inca sites extend northward along the Chinchaysuyu branch of the Qhapaq Ñan, encompassing Chincherro, Killarumioc, Tarawari, Choquequirao, Saywite, Vilcabamba, Huánuco Pampa, and Aypate. The chronicles describe the construction of “tambos” as outposts along these routes, for administrators to collect taxes, to house their troops, and to store food and supplies. These Inca sites become less frequent the farther they are from Cusco, as expected if those territories were captured later in their history.

The Inca first conquered parts of Ecuador under Topa Inca Yupanqui, with further expansion under his successors. When the Spanish arrived, their empire was divided by civil war between two rival half-brothers. This northern territory was held by Atahualpa, whereas Huáscar held Cusco and the south.

In Ecuador we find Ingapirca, which shares key characteristics of other Incan sites. It was originally a Cañari religious center. While the Inca honored a pantheon of deities and oracles, they primarily worshipped the Sun, viewing their ruler as its divine human incarnation. They allowed conquered peoples to continue worshipping their local deities, but often constructed Temples of the Sun within captured territory. At Ingapirca, they built a curved-walled Sun Temple, reminiscent of Cusco's Qoricancha and Machu Picchu's solar observatory. All three temples are constructed with coursed-ashlar masonry. Here we also see the distinctive Inca architectural elements of double-jambed entryways with trapezoidal doors, windows, and niches.

These Inca-attributed sites do map well relative to the expansion of the Inca Empire, particularly those concentrated around Cusco. Not only do they fit both the territory held by the Inca at the time of the Spanish conquest, but also the Inca’s oral history and radiocarbon dating studies to within a few decades of each other.

What then is the alternative-history explanation for how this could have happened? If the Inca merely found these sites and pretended that they were their own, why does this architectural distribution mirror the extent of their empire? Why are the best examples of this stonework concentrated around Cusco, the Inca capital? Is it simply coincidence that the largest known empire to sweep across South America happens to have the same distribution as their alleged lost ancient civilization? Or, using Occam's Razor, is the simpler explanation that the Inca built them as their massive empire expanded?

One final argument from alternative-history proponents is that the Inca supposedly told the Spanish they didn’t build these sites. This is false. Many of the citations listed above have already demonstrated the opposite – the Inca consistently described constructing them. This misunderstanding originates from Graham Hancock’s pseudo-archeological book Fingerprints of the Gods, where he misrepresents a passage from Cieza de León. In the original account, the Spaniard is asking locals at Lake Titicaca about the Tiwanaku ruins:

“There are other things to tell of Tiahuanacu [Tiwanaku] which I omit to save time. In conclusion, I would say that I consider this the oldest antiquity in all Peru. It is believed that before the Inca’s reigned, long before, certain of these buildings existed, and I have heard Indians say that the Incas built their great edifices of Cusco in the form that they saw of the wall of this town." … “I asked the natives … if these buildings had been built in the time of the Inca, and they laughed at the question, repeating what I have said, that they were built before they reigned, but that they could not state or affirm who built them. However, they had heard from their forefathers that all that are there appeared overnight. Because of this, and because they also say that bearded men were seen on the island of Titicaca [ie. the legend of Tici Viracocha] and that these people constructed the building of Vinaque, I say that it might have been that before the Incas ruled, there were people of parts in these kingdoms, come from no one knows where, who did these things, and who, being few and the natives many, perished in the wars.”

- Pedro Cieza de León (1518-1554), The Chronicles of Peru (1553)

While the Tiwanaku ruins do indeed predate the Inca by centuries, that is because that particular site was constructed by the Tiwanaku culture during the Intermediate Period. It has nothing to do with the many later Inca sites. Elsewhere in his chronicle, Cieza de León records similar remarks about the Wari ruins in Huamanga / Ayacucho (the Wari's former capital city), again referencing a known earlier culture. Both the Tiwanaku and the Wari were important predecessors to the Inca with their own monumental architecture. Cieza de León even notes that the Inca borrowed some masonry inspiration from Tiwanaku. For example, they experimented with metal clamps within walls at Qoricancha and Ollantaytambo, a technique also seen at Pumapunku.

Apart from the earlier radiocarbon dating, Wari and Tiwanaku architecture differs significantly from Inca stonework. Wari and Tiwanaku stonework lack both the Inca style lifting bosses and none of it is in the tight-fitting polygonal joints. Those sites are clearly from a different culture. Cieza and the other chroniclers do also record the Inca history of constructing sites like Sacsayhuaman, Qoricancha, and Cusco — quotes that Hancock and other alternative-history theorists conveniently overlook.

Conclusion: The “Secret” Behind the Incas’ Monumental Architecture

Taken together, the historic record, physical evidence, and radiocarbon dating all converge upon one unified understanding of Inca stonemasonry prowess. Not only was this legacy recorded by the Spanish chroniclers, but the exceptional native masonry work was directly observed during the early colonial period. The secret behind how this was done isn’t some long-forgotten advanced technology. It’s not the work of some mythical ice-aged civilization. And it’s not some magical ability to soften various varieties of stone. The simple truth is that the Inca had some of the most talented stonemasons in human history.

To summarize what is known of their masonry techniques:

• They constructed ramps to both transport and place the stones.
• Their ichu grass ropes were strong enough to pull the stones, with the thickest able to hold tens of thousands of pounds.
• “Tired stones”, left in transit, show how they were dragged along specially prepared roads.
• Large rocks were split along chiseled-out rows of holes for wedges.
• They used simple yet effective tools, such as hammerstones of various sizes, plumb-bobs, stone chisels, bronze cold-hammered chisels, and prybars.
• Hammerstone impact marks can be seen on the surface of the stones, while rock chips deposited below walls further confirm their use.
• Blocks were often slightly wedge-shaped, joined mainly along their rising edge faces, with gaps between them packed with clay.
• Multiple Spanish chroniclers speak of the fitting of stones being a tedious and repetitive process, requiring multiple adjustments for a perfect fit.
• The positioning of nubs and damage on their undersides indicates most were used as lifting bosses, useful for tilting back stones while shaping them to fit.
• These lifting bosses were then generally removed after fitting, during the final stone dressing process.

Beyond these methods, what made this all possible was manpower, determination, and logistics. While technologically, their masonry methods were deceptively simple, the emphasis instead should be upon the Incas’ ability to marshal resources for projects on this massive scale. They had one of the world’s largest empires at the time of the Spanish arrival. With a peak population of over ten million to draw from, they had ample resources to build these monuments. And their mit’a system obligated conquered subjects to pay tribute in the form of food and labor, tracked by regional administrators with quipus.

Sketches by Felipe Guaman de Ayala (1535-1616), a Quechua nobleman and missionary who documented Inca life during the post-colonial period.

To maximize the productivity of their expanding territory, they transformed the landscape by building terraced fields and irrigation canals. They guided the domestication of hundreds of varieties of crops. A vast network of roads was established, traveled by long caravans of llamas hauling goods between their tambos. And they built colcas (high altitude food storage facilities) where cooler air preserved food supplies. This entire system allowed them to feed the tens of thousands laboring on their various construction projects. This was the true source of the Incas’ power, the overlooked secret behind how these monuments were constructed. None of these megalithic sites would have been possible if it weren’t for their mastery over agriculture and logistics.

"[Pachacuti Inca Yupanqui] wanted the lands to be improved so that perpetually they and their descendants could farm and be supported... Soon the cacique lords counting with their quipus, which means numerical record, brought him the total number of Indians they had... he ordered each one of those of Cusco who had been lucky enough to get lands to go out and improve them, making canals for irrigation, all of which was repaired and made from building stones so that the construction would last forever. ... he told them that it was urgent that in the city of Cusco there be storehouses for all foods... Making these storehouses and preparing the land for them took five years because they made a great many storehouses... This food he had there was also for those whom he wanted to make stone structures in the city of Cusco and repair the rivers that run through it. He thought that, by itself having such a large amount of provisions, none would be lacking to feed the men he wanted to have construct the buildings and houses he wanted rebuilt.”

- Juan de Betanzos (1510-1576), Narrative of the Incas (1576)

Inca stonework truly is extraordinary. It would have been even more so to see these historic sites in person before they began to be dismantled by the Spaniards. Fortunately, the early chroniclers left detailed descriptions of what they saw. While some alternative-history theorists will continue to promote their unsupported lost civilization narrative, the evidence overwhelmingly shows that these megalithic sites were orchestrated by the Inca themselves. To attribute these works to an unknown lost civilization, for which there is no evidence, only diminishes the rightful legacy of the Inca’s master architects and stonemasons.

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