El Castillo (The Kukulkan Pyramid)
Possibly the best known construction on Chichen Itza is Kukulkan's Pyramid.
El Castillo (The Kukulkan Pyramid), a square-based, stepped pyramid that is approximately 75 feet tall.
Kukulkan Pyramid was built for astronomical purposes and during the vernal equinox (March 20) and the autumnal equinox (September 21) at about 3pm the sunlight bathes the western balustrade of the pyramid's main stairway.
This causes 7 isosceles triangles to form imitating the body of a serpent roughly 37 yards long that creeps downwards until it joins the huge serpent's head carved in stone at the bottom of the stairway.
Mexican researcher Luis El Arochi calls it "the symbolic descent of Kukulkan" (means the feathered serpent), and believes it could have been connected with agricultural rituals.