Officers react at their graduation ceremony during Iraqi Army Day anniversary celebration in Baghdad January 6, 2015. Iraqi Defence Minister Khaled al-Obeidi said on Tuesday that the Iraqi military has started rebuilding after its near total collapse last summer but that the effort is still in its initial phase. (Photo by Ahmad Mousa/Reuters)

The abandoned Moulton and Kyle Funeral Home in Jacksonville, Fla., which is more than 150 years old, was left to rot, with the premises eerily strewn with open caskets, a hearse and embalming chemicals. Much like the corpses that were laid to rest, the remains of this building too are slowly decomposing and decaying. Black mold has engulfed the walls, and chipped tiles from the collapsed ceilings cover many of the floors. (Photo by Abandoned Southeast/Caters News Agency)

A local boy plays football on Iracema Beach on June 11, 2014 in Fortaleza, Brazil. (Photo by Robert Cianflone/Getty Images)

A client reacts as she is tattooed during the Tattoo Week SP 2016 in Sao Paulo, Brazil, July 23, 2016. (Photo by Paulo Whitaker/Reuters)

People see in the new year at Copacabana beach in Rio de Janeiro, Brazil on January 1, 2024. (Photo by Reuters/Stringer)

Women pose for a selfie at Ipanema Beach in Rio de Janeiro, Brazil on July 30, 2016. (Photo by Nacho Doce/Reuters)

Russian fashion model Irina Shayk bares it all while getting ready for the Rio Carnival parade in Brazil early March 2025. (Photo by irinashayk/Instagram)

A cenote is a natural phenomenon, a sinkhole in the Earth’s surface. The Yucatan Peninsula in Mexico has an estimated 7,000 cenotes because it 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. The water found in a cenote may be fresh water, salt water, or both. Structurally it may be completely open, like a lake, almost completely closed with just a small opening at the top, or somewhere in between.