Following a long path from the Kulkulcan Pyramid you get to the Sacred Cenote, a natural waterhole where religious and social rituals took place.
Some of the rituals involved the sacrifice of young girls and warriors, but this practises were not as commons as once thought.
The name of Chichen Itza refers to this cenote. "Chi" means mouth, "Chen" well, and Itza is the name of a water deity; altogether the "mouth of the well of the Itza."