Located in the Yucatan Peninsula, Chichen Itza was a large city built by the Mayans around 600 A.D. It thrived until about 1221 when the power in the region shifted, and then it was abandoned completely in the 1400s.
The most recognized structure in Chichen Itza is the Temple of Kukulkan, also known as El Castillo. It is a pyramid that was built with heavy influence from the astronomy of the time. It has 365 steps: one for each day of the year. Twice a year, a shadow falls on the pyramid in the shape of a serpent, which marks the spring and autumn equinoxes. As the sun sets, the shadow serpent descends the steps to a stone serpent head at the base of the pyramid. The Mayans were also able to predict solar eclipses with the pyramid.