The astounding remains of Sacsayhuamán stand on top of a hillside overlooking Cuzco. They comprise a series of three ramparts of huge blocks of granite, linked by stairways and trapezoidal doors and demarcating three superimposed platforms. As for the site's purpose - whether defensive, religious or for stargazing - it is difficult to ascertain. Every year on 24 June, the Incan Inti Rayni folklore festival in celebration of the sun is held here.