Constructed during the reign of Pachacuti (1438-1471 CE), Sacsayhuamán was a fortress complex in Cusco, the former capital of the Inca Empire. The earliest structures at the site were made of mud and clay while the later ones constituted great examples of the Incan workmanship. These new structures consisted of several megaliths mostly over 4 meters high and weighing over 100 tons.

Sacsayhuamán fortress was the largest structure built by the Incas.

In order to create such smooth megaliths, the Incas only used harder stones and bronze tools. They also used ropes, logs, levers, and earthen ramps to move these massive stone blocks. Although experimental archaeology proved that shaping these stones is quicker than one may thought, it still must have taken the Incas several months to complete a wall. The Incas also took earthquakes into consideration by interlocking the stone blocks and constructing the walls with a certain slope. Therefore, the fortress complex got little damage from the earthquakes of the last 500 years.

As for its design, the complex has three terraces with zigzag walls, stretching over 540 meters and reaching 18 meters in height. The walls’ form actually mimics the form of the mountain range stretching at the horizon behind the fortress. It is because the Incan architects paid special attention to integrating the structure with the surrounding landscape. On the sliding part of the fortress hill, there were more terraces, outbuildings, and a water supply system consisting of cisterns and aqueducts. Finally, there was a platform over the hill that could be a temple, probably dedicated to the earth goddess Pachamama, or an area for astronomical observations.