Boats of fishermen are seen on the dried Poopo lakebed in the Oruro Department, south of La Paz, Bolivia, December 17, 2015. Lake Poopo in Bolivia, the Andean nation's formerly second largest after the famed Titicaca, has dried up entirely. With the water now gone, animals have died off in the millions, according to studies. And the local families, having lost much of their sustenance, have been forced to migrate. (Photo by David Mercado/Reuters)

British visitors wearing Bavarian costumes walk ahead the opening of the traditional Bavarian Oktoberfest festival at the Theresienwiese in Munich, southern Germany, on September 20, 2014. Germany's world-famous Oktoberfest kicks off with millions of revellers set to soak up the frothy atmosphere in a 16-day extravaganza of lederhosen, oompah music and, of course, beer. (Photo by Karl-Josef Hildenbrand/AFP Photo/DPA)

“Catasta” wearing a latex hexus costume poses in the grounds of St Mary's Church during the “Whitby Goth Weekend”, North Yorkshire, on November 2, 2014. The event grew out of the punk scene in 1984 with its own style of music and fashion. The event in Whitby now attracts Goths from all over Europe and creates over 1 million pounds in revenue for local busnisess. (Photo by Anna Gowthorpe/PA Wire)

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.

Women perform square dancing at a park square in Beijing, China, April 9, 2015. Chinese-style square dancing is running circles around other hobbies for the elderly, with millions taking to parks and plazas across China, swivelling their hips and rolling their arms – but it's not to everyone's liking. (Photo by Kim Kyung-Hoon/Reuters)

Labourers use a crane to lift the hand of a giant bronze statue of former King Rama I at Ratchapakdi Park in Hua Hin, Prachuap Khiri Khan province, Thailand, August 4, 2015. The park is being constructed by the Thai army to honor past Thai monarchs and is situated on an army compound near the Klai Kangwon Palace. The project is estimated to cost about 700 million baht ($20,000,000), according to local media. (Photo by Athit Perawongmetha/Reuters)

School children celebrate after being rewarded for their dance performance during India's Independence Day celebrations in Chandigarh, India, August 15, 2015. Indian Prime Minister Narendra Modi's independence day speech focused on measures his “Team India” had rolled out to include millions of poor Indians in the banking and insurance systems, policies for workers and farmers and successes in the fights against inflation and corruption. (Photo by Ajay Verma/Reuters)

Spectators using virtual reality glasses at the “Los Ultimos Dias De Pompeia” Exhibition at Matadero on September 06, 2023 in Madrid, Spain. (Photo by Borja B. Hojas/Getty Images)