Cenotes are natural pits or sinkholes resulting from the collapse of limestone bedrock that exposes groundwater underneath. They are especially associated with the Yucatán Peninsula of Mexico, which is primarily made up of porous limestone. For millions of years, rainfall slowly ate away at the limestone and a huge system of underground caves and caverns was formed. Many filled with water from rain or from the underground water table. When the roof of a water filled cave collapses, a cenote is born. There are an estimated 7,000 cenotes in the Yucatán Peninsula.
Cenote comes from the Mayan word “dzonot” or “ts’onot” which means sacred well, and had great significance for the Maya. First, they represented the main water supply in a land that has no surface water bodies and suffers long dry seasons. As a consequence, all Mayan villages were built in the vicinity of a cenote, in order to secure a permanent water supply. Second, cenotes were also important for religious reasons. They believed cenotes to be portals to the underworld and a way to communicate with the gods. Archaeological research has found evidence of religious ceremonies that took place in or around cenotes, including human sacrifices.
While the best-known cenotes are large open water pools measuring tens of meters in diameter, such as those at Chichén Itzá, the greatest number of cenotes are smaller sheltered sites and do not necessarily have any surface exposed water.
Cenote water is often very clear, as the water comes from rain water filtering slowly through the ground, and therefore contains very little suspended particulate matter. This have attracted swimmers and cave divers from around the world who have documented extensive flooded cave systems, some of which have been explored for lengths of 100 km or more.
Some cenotes have been turned into public swimming pools of sorts. One of the best examples is the Cenote Zaci, located in Valladolid. Another cenote with some tourist infrastructure is the Cenote San Ignacio, in Chochola. This cenote is artificially lit and has an adjoining restaurant and other services that make for a more comfortable visit. Finally, the facilities at Cenote Sambula, in Motul, were recently remodeled.