A cenote is essentially a sinkhole that is formed when the ceiling over an underground river collapses, creating a freshwater pool. Since the entire Yucatan Peninsula was under water less than a million years ago, the foundation of the land here is mainly comprised of limestone covered by a thin layer of topsoil, which allows the ground water to sink down to form underground rivers.
Cenotes have been important to the development of humankind in the region since the ancient Maya built great civilizations here, with many of their cities located very close to a cenote. As the only source of water in the area, they were important for not only for survival – both in terms of drinking and irrigation – but also for various religious ceremonies. In the large cenote near the large Mayan city of Chichén Itzá, for example, divers have found a variety of offerings thought to have been made to the gods, including copper and gold necklaces, pottery, skeletons and jade. In fact, early explorers in the region were surprised at the cultures focus on and fascination with water, since the region has no above ground rivers or lakes and experiences a substantial annual dry season. This actually makes sense, since the acquisition of fresh water was crucial to survival, explaining why the Mayan water god was a favorite decoration for ancient temples and other structures.
Types of cenotes include the more mature cave variety, which is home to a large amount of interior stalactites and stalagmites, as well as the younger variety, which has recently been exposed after the ground (which is also the roof of the underground river) suddenly crumbled and revealed their existence. In addition, some mature cenotes have dried out from evaporation, which often causes the bottom to fill up with mineral deposits that are the result of calcium salt precipitation, while others are completely dry and filled with a variety of residues – from mineral to organic.
To date,more than 1,000 cenotes have been discovered on the Yucatan Peninsula, but more than 4,000 are believed to exist. They have not lost their appeal in modern times, becoming a major attraction for tourists and residents alike, thanks to their impressive archaeological value and stunning natural beauty.