Residents recently returning to their area cleared by government troops react as they ride a tricycle a day after President Rodrigo Duterte declared the liberation of Marawi city in southern Philippines Wednesday, October 18, 2017. Sporadic explosions continue Wednesday as Philippine soldiers fought to gain control of the last pocket of Marawi controlled by Islamic militants. (Photo by Bullit Marquez/AP Photo)

An Chelsea supporter takes pictures next to the giant inflatable replica of the UEFA Champions League trophy placed at Aliados Avenue in Porto, Portugal, 27th May 2021. Porto hosts the UEFA Champions League final between Manchester City and Chelsea in 29th May 2021. (Photo by Jose Coelho/EPA/EFE)

The buildings of the banking district are seen through thousands of rain drops on a glass railing in central Frankfurt, Germany, Wednesday, January 11, 2017. (Photo by Michael Probst/AP Photo)

A man is seen wrapped with pythons, some which include the Albino Burmese Python, as part of a show celebrating the coming Year of the Snake in the Chinese calendar, while spectators look on, in Malabon city, north of Manila, Philippines, December 28, 2012. (Photo by Romeo Ranoco/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.

Loreen from Sweden performs after winning the 2023 Eurovision Song Contest in Liverpool, Britain on May 14, 2023. (Photo by Phil Noble/Reuters)

A woman dries chili peppers in the sun at a village in Wuyuan County, Jiangxi province, China July 21, 2017. (Photo by Reuters/China Stringer Network)

Dinosaur costumed actors representing Thailand's establishment at a high school student led protest in Bangkok, Thailand on November 21, 2020. (Photo by Matthew Tostevin/Reuters)