1. Sacsayhuaman
Overlooking the city of Cusco in Peru is the archaeological site of Sacsayhuaman. Known for its large stone structure that sits at an altitude of 12,000 feet, this ancient citadel was built during the 13th century by the Inca. Many researchers are still baffled at how the Inca could move and position the large boulders that make up the perimeter of the citadel, and it’s still unknown what the entire structure was used for. However, some believe it’s possible that part of the site was used for religious rituals.