Sacsayhuaman is a huge complex that would take several days to fully explore. It is known for its series of walls built out of extremely large, black rocks. Some of the larger rocks can weigh up to 125 tons. It is said that the walls used to be much higher, before the Spanish used the stone in order to build cathedrals in their colonial city. Sacsayhuaman is found outside of Cusco and was built by a Pre-Incan culture around 1100 A.D.