Leaning against the stone wall at the foot of what was once an Inca palace in Cusco, posing for a photograph like millions of tourist before me, I notice how the huge rocks fit together along five or more sides. It would be a Herculean task to build this wall, and it would be just as hard to take the wall apart.

Sacsayhuaman, Cusco

Sacsayhuaman, Cusco

The Spanish Conquistadors learned this the hard way after demolishing as many Inca buildings as they could. When it came to these massive foundations they ran out of energy.

The cornerstone of Inca culture is literally their stone construction methods. No other culture in history ever took the same ingenious approach of forming rock into polygonal shapes, fitted together precisely and permanently.

Their exacting methods fit blocks together so tightly that even the thinnest blade cannot slide between them. Cutting the blocks into multi-sided shapes, no two identical, allowed Inca builders to position their structures onto almost vertical landscapes, and to integrate them into the form of the mountains.

Ollantaytambo incan stone masonry

Probably the best stone masons in the world!

Polygonal shaped building stones have another great advantage, especially in this part of the world that is prone to seismic activity. These blocks are interwoven in a way that makes them all but impervious to earthquakes. They can take a strong shaking. The non-symmetrical multiple panes are notched together, so tightly they are almost impossible to dislodge. In fact they lodge together even more tightly in an earthquake.

Inca stone masons used a technique of fitting called scribing. Stone blocks were positioned above their final resting place. The edges of the stone, and the ones around it, were scored and then cut to notch together, creating a lock tight surface.

Stone cutters would follow natural fractures in the rock crystal, individualizing each building block to match its neighboring blocks. The result is the asymmetrical harmony of angles that is instantly recognizable as Inca construction.

Chisels fashioned from denser stone, and from bronze and copper, were used. Additionally the Incas took advantage of natural fractures in the stone wherever possible. They poured boiling water into cracks and drilled holes and used wedges to cut the rocks to shape.

Temples, palaces and royal and ceremonial buildings got special treatment. The visible surfaces were finished to a smoothly shinned polish using sand and abrasive stone pads.

Most buildings, whether they were residences or public spaces had interior corners that were squared, regardless of the exterior shape. To achieve this, inside walls were dressed with plaster, and then painted.

Doorways and windows were always trapezoid shaped; four unparallel sides, narrower at the top to spread the weight of the wall over the frame. Door covers were wooden. The hinges were carved of wood, or on important buildings, stone. Some windows had wooden covers, but most were fabric covered, admitting the light.

Most Inca buildings began with a really solid and level foundation. The ground was excavated and flattened wherever possible, and the largest blocks set as a base. These sound foundations combined with the interlocking polygonal blocks account for the enduring strength of their structures.

Despite the heavy stone footings and walls, the Incas never devised a system of durable roofs. They used thatched reed fastened onto wooden supports with rope. The reeds was replaced every couple of years. No Inca structure survives with its roof.

The iconic Machu Picchu

The iconic Machu Picchu

Most Inca buildings were a single story. The exceptions being towers built as military observation posts, multi-story temples and a few palaces with two or three floors. Stairs, which were more commonly built along the roads, were made of overlapping stone blocks.

Standing by the Inca wall, damage from the 1950 earthquake is still visible on the cathedral across the square. Replacement bricks on the bell tower don’t quite match, and iron support struts have been added to reinforce the sides. Three centuries earlier in 1650 an even stronger earthquake leveled almost every colonial building in Cusco, Peru. But the massive rocks of the Inca foundations have remained unmovable and timeless.

Born in The Hague, Andrew Kolasinski arrived in Canada as a small child riding in the luggage rack of a DC-7. Since then he has felt at home anywhere. As the publisher and editor of Island Angler, Andrew spends half the year fishing for salmon and trout, and in the off-season he travels the world looking for a story. He wrote this article for Aracari Travel, experts in providing personalized tours in Cusco and all over Peru.