An Afghan girl harvests Cotton buds at a field on the outskirts of Balkh province, Afghanistan, November 15, 2014. (Photo by Sayed Mustafa/EPA)

A tree covered with hoarfrost casts a shadow on a snowy field, shot with a drone in Sieversdorf-Hohenofen, Germany on January 31, 2021. (Photo by Patrick Pleul/dpa)

A monolith placed in the Utah wilderness in November 2020. New clues have surfaced in the disappearance of the gleaming monolith that seemed to melt away as mysteriously as it appeared in the red-rock desert. A Colorado photographer told a TV station in Salt Lake City that he saw four men push over the hollow, stainless steel structure last Friday night. (Photo by Terrance Siemon/AP Photo)

A woman hangs strips of salted meat she collected from different places during the Muslim's Eid al-Adha or Festival of Sacrifice, in Lahore, Pakistan, Sunday, August 2, 2020. Pakistanis are celebrating the Eid al-Adha, or the Feast of the Sacrifice, to mark the willingness of the Prophet Ibrahim – Abraham to Christians and Jews – to sacrifice his son. During the holiday Muslims slaughter sheep and cattle, distribute part of the meat to the poor. (Photo by K.M. Chaudary/AP Photo)

Jordan Mann (R) falls into the water as he and Jordan Cross compete in the first round of Men's 3000 Meters Steeplechase during day four of the 2020 U.S. Olympic Track & Field Team Trials at Hayward Field on June 21, 2021 in Eugene, Oregon. (Photo by Patrick Smith/Getty Images)

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.

A girl walks along rice paddy fields during “National Paddy Day”, which marks the start of the annual rice planting season, in Tokha village on the outskirts of Kathmandu on June 29, 2020. Splashing mud and drinking local rice beer, Nepali farmers this week celebrated National Paddy Day to mark the beginning of the rice-planting season, despite some coronavirus lockdown measures still in place. Traditional farming songs and laughter echoed in the air as farmers waded into waterlogged fields to sow green paddy. (Photo by Prakash Mathema/AFP Photo)

Women, wearing traditional “ao dai” dress, pose for a photo next to peach blossom flowers ahead of Vietnamese “Tet” (the lunar new year festival) in a field in Hanoi January 22, 2017. (Photo by Reuters/Kham)