Located in the center of the Great Plaza stands the Temple of Kukulkan, also referred to as El Castillo (the castle in Spanish). Dedicated to the feathered serpent god Quetzalcoatl, this is easily the most famous landmark of Chichén Itzá. The pyramid rises 79 feet (24 meters) above the plaza, plus an additional 20 feet (6 meters) for the temple on top. The base of the pyramid is 181 feet (55.3 meters) on each side. El Castillo represents the Snake Mountain, a mystic place in Maya folklore where creation first occurred. Snake Mountain is a design practice adopted in Teotihuican as well as the Aztec capital of Tenochtitlan. At Chichen Itza the design is brought to its full artistic maturity.
The Maya were great mathematicians, inventing the concept of “zero” long before western civilizations. They were also great astronomers, and El Castillo is the perfect marriage of these two sciences. The temple contains many references to the important Mayan calendar. Each of El Castillo’s four sides has 91 steps which, when added together and including the temple platform, equals the 365 days of the solar year. Each of the nine terraces are divided in two, which makes 18, symbolizing the number of months in the Maya calendar. The terraces contain a total of 52 panels, referring to the 52-year cycle when both the solar and religious calendars converge.
On the corners, the staircases have railings with carved feathered serpents, the open-jawed head at the foot and the rattle held high at the top. During the spring and autumn equinoxes, at the rising and setting of the sun, the corner of the pyramid casts a shadow in the shape of a snake, representing the god Quetzalcoatl. As the sun moves, the serpent slowly descends into the earth.
During restoration of El Castillo in the late 1920s and early 1930s, archaeologists discovered it had been built upon an earlier temple. Researchers estimated that this construction dates to the 11th century AD. Today a small doorway under the northern staircase leads to a small stairway into a temple within the pyramid. In this inner temple a Chac Mool statue and a jaguar throne were found. Visitors are not allowed to go inside however. As of January 2006, it is also no longer allowed to climb El Castillo.