Iraqi soldiers work at a radio station at Makhmour base, Iraq April 17, 2016. The Iraqi army has set up a radio station at its base in Makhmour broadcasting into areas south of Mosul controlled by Islamic State militants. The radio, which reaches villages halfway to the northern city, broadcasts military anthems and messages to the more than one million civilians living there. Radio operators said their aim was to weaken the militants’ morale and reassure civilians that the military has not forgotten them after nearly two years under Islamic State control. (Photo by Ahmed Jadallah/Reuters)

Dancers Marion Krebs and Judy Ness, right, pose as batter and catcher in front of the Chicago White Sox dugout before start of game with Detroit at Comiskey Park, Chicago, Ill., September 18, 1959. White Sox won, 1-0, to move within two games of clinching the American League pennant. (Photo by AP Photo)

A picture released by the North Korean Central News Agency (KCNA) shows Kim Jong-un convening an urgent operation meeting at 0:30 am on March 29, 2013 at an undisclosed location, in which he ordered strategic rocket forces to be on standby to strike US and South Korean targets at any time. (Photo by KCNA via EPA)

Midfielder Lindsey Horan (9) of Team United States and midfielder Kosovare Asllani (9) of Team Sweden go up for a header during the first round of the Tokyo 2020 Olympic Games at Tokyo Stadium on Wednesday, July 21. 2021. Sweden defeated the United States of America 3-0. (Photo by Toni L. Sandys/The Washington Post)

Roma's Gianluca Mancini scores his team's goal in the 1-0 Rome derby victory over Lazio at Stadio Olimpico in Rome, Italy on April 6, 2024. (Photo by Alberto Lingria/Reuters)

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.

Asia Sawicka as Anastasia IV poses for a photograph prior to a rehearsal of the Circus of Horrors' latest show Voodoo, ahead of Halloween, at the Wookey Hole Caves Theatre near Wells on October 19, 2017 in Somerset, England. (Photo by Matt Cardy/Getty Images)