Educational tour @ Cenote Ik-Kil in Cancun, Mexico
Cenote, is a naturally formed pit or sinkhole made of limestone. The Yucatan Peninsula, including the Riviera Maya, has a vast river system that flows underground throughout the area. Over the course of the centuries, portions of caverns and the the limestone roof that supports the waterways has weakened, and in some places collapsed, creating cenotes. For the ancient Maya, cenotes were their only source of fresh water. Mayan cities were built around a cenote for the sole purpose of a water source, and today, cenotes are used for daily water sources. In addition to a water source, cenotes were considered to be "sacred wells" where religious ceremonies often took place. Cenotes are the entrance into the underworld, the most sacred place for the Maya. But the Cenote Sagrado with 60 meters in diameter inside the city of Chichen Itza, is a dumping area for many dead bodies of prisoners, criminals, enemies and losers - human offerings (see the Apocalypto 2006 movie) in addition to cremating their dead bodies to avoid diseases or feeding their heads hanging in every post to the eagles and jaguars as well.