A feat of geological engineering
The Saksaywaman complex, at an altitude of 3,701 meters (12,142 ft), is a large-scale dry stone masonry. The three parallel, zigzagging walls are built from massive blocks of limestone and andesite porphyry. The largest of these stones are estimated to weigh between 128 and 200 tons. The longest of the three walls runs for about 400 meters, and the walls are roughly 6 meters tall. The total volume of stone in the structure exceeds 6,000 cubic meters.
Construction, which began in the 15th century under the Inca emperor Pachacuti, involved quarrying and shaping these immense blocks using only harder stones, such as hematite, and bronze tools. The builders transported the stones from quarries as far as 35 kilometers (22 miles) away. Experiments suggest that moving even a 10-ton block would have required more than 100 men pulling ropes. The Inca shaped the blocks using a technique of scribing and pounding, allowing them to fit the irregular stones together perfectly without any mortar. The precision is so exact that in many places, a single piece of paper cannot be inserted between the stones. This style, known as polygonal masonry creates a wall that interlocks like a complex, three-dimensional puzzle.
An earthquake-resistant design
Saksaywaman's construction provides exceptional resistance to seismic activity, a common threat in the Andes. In a technique now called "ashlar masonry," the lack of mortar and the incredibly tight fit allow the stones to move and "dance" during an earthquake. This flexibility lets the structure absorb and dissipate seismic energy, after which the blocks settle back into their original positions. This is a main reason why Saksaywaman has survived centuries of earthquakes that have destroyed many Spanish colonial buildings in Cusco.
The engineering principles extend to other features. The walls lean inward by 3 to 5 degrees, and doorways are built in a trapezoidal shape, wider at the base than at the top. These geometric choices lower the structure's center of gravity and provide additional stability against tremors. While its defensive appearance led the Spanish to believe it was a fortress, archaeologists have found evidence of ceremonial use, suggesting it served both military and religious functions. The zigzag pattern of the walls may have been a defensive strategy to expose the flanks of attackers, or it represents the teeth of a puma, a sacred Inca animal.