Chichén Itza

Dominating the center of Chichén Itza is the Temple of Kukulkan (the Maya name for Quetzalcoatl), often referred to as "El Castillo" (the castle). This step pyramid has a ground plan of square terraces with stairways up each of the 4 sides to the temple on top. On the Spring and Fall equinox, at the rising and setting of the sun, the corner of the structure casts a shadow in the shape of a plumed serpent - Kukulcan, or Quetzalcoatl - along the side of the North staircase. On these two days, the shadows from the corner tiers slither down the northern side of the pyramid with the sun's movement. The pyramid has 91 steps each in 4 faces. The top of the pyramid has 1 step so that the total of the steps are 91x4+1=365 which are equal to the days in a year.