The cenote is a natural formation, a karst cave tunneled into the limestone by moving groundwater, after which the ceiling collapsed, creating an opening at the surface. The opening of the Sacred Cenote is about 65 meters in diameter (and about an acre in area), with steep vertical sides some 60 feet above the water level. The water continues for another 40 feet and at the bottom is about 10 feet of mud.
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 in times of droughts (actually Bishop Landa reported the sacrificial victims were virgins, but that was probably a European concept meaningless to the Toltecs and Maya at Chichén Itzá). Archaeological evidence supports the use of the well as a location of human sacrifice. At the turn of the 20th century, American adventurer-archaeologist Edward H. Thompson bought Chichén Itzá and dredged the cenote, finding copper and gold bells, rings, masks, cups, figurines, embossed plaques. And, oh yes, many human bones of men, women and children. Many of these objects are imports, dating between the 13th and 16th centuries AD after the residents had left Chichén Itzá; these represent the continued use of the cenote up into the Spanish colonization. These materials were shipped to the Peabody Museum in 1904, and repatriated to Mexico in the 1980s.