The amazing remains of Sacsayhuamán stand on top of a hillside overlooking Cuzco: huge blocks of stone, some of which weigh several hundred tons, perfectly embedded one into the other, form what look like ramparts and a cluster of round-shaped buildings. What was the site's purpose? Defensive, religious, star gazing – who knows? The site comes back to life every year on June 24 during the Incan Inti Rayni folklore festival in celebration of the sun.