Sacsayhuamán (also known as Sacsahuaman) is a walled complex near the old city of Cusco, at an altitude of 3,701 m. or 12,000 feet. The site is part of the City of Cuzco, which was added to the UNESCO World Heritage List in 1983.
They are three parallel walls built in different levels with lime-stones of enormous sizes. Zigzagging walls are made of boulders used for the first or lower levels are the biggest; there is one that is 8.5 m high (28 ft.) and weights about 140 metric tons. Those boulders classify the walls as being of cyclopean or megalithic architecture.
There are no other walls like these. They are different from Stonehenge, different from the Pyramids of the Egyptians and the Maya, different from any of the other ancient monolithic stone-works. Scientists are not certain how these huge stones were transported and processed to fit so perfectly that no blade of grass or steel can slide between them. There is no mortar. The stones often join in complex and irregular surfaces that would appear to be a nightmare for the stonemason.
The site remains a real unsolved ancient mystery