Chichen Itza was a large pre-Columbian city built by the Maya people of the Post Classic.
"The heart of Chichén Itzá is the Sacred Cenote, dedicated to the Chac God, the Maya God of rain and lightening. Located 300 meters north of the Chichén Itzá compound, and connected to it by a causeway, the cenote was central to Chichén, and in fact the site is named after it--Chichén Itzá means "Mouth of the Well of the Itzas". At the edge of this cenote is a small steam bath.
The use of this cenote was exclusively sacrificial and ceremonial; there is a second karst cave (called the Xtlotl Cenote, located in the center of Chichén Itzá) that was used as a source of water for Chichén Itzá's residents. According to Bishop Landa, men, women and children were thrown alive into it as a sacrifice to the gods."
source : (
visit link)
The opening of the Sacred Cenote is about 65 meters in diameter, with steep vertical sides some 60 feet above the water level.