Soyuz MS-12 spacecraft with crew members of Expedition 59/60 Russian cosmonaut Alexey Ovchinin, NASA astronauts Christina Koch and Nick Hague lifts off from the launch pad at the Russian leased Baikonur cosmodrome, Kazakhstan, 15 March 2019. Hague, Koch, and Ovchinin will spend six-and-a-half months living and working aboard the International Space Station. (Photo by Sergei Ilnitsky/EPA/EFE)

The Milky Way rising above Durdle Door in Dorset, United Kingdom on Saturday night, March 18, 2023. The image consists of 19 two-minute exposures, ten of the foreground and nine of the sky which needed a motorised star tracker to ensure the Milky Way wasn't blurry. All the photos were merged together to reveal more detail than what the naked eye can see. (Photo by Nick Bull/Picture Exclusive)

Young women walk through the cave of Saint George during Ashenda festival, at Saint George Church, in Lalibela, Ethiopia, on August 22, 2022. (Photo by Amanuel Sileshi/AFP Photo)

At this year’s Venice Bienniale in Italy, the Korean pavilion has a curious exhibit called “Commissions for Utopia”. It includes renderings from North Korea’s top architects and artists (all anonymous), many of whom studied at the Paekho Institute of Architecture, North Korea’s state-run architectural college, and none of whom have ever left the country. They were asked to create a vision of North Korea’s future sustainable architecture for its expanding tourism industry. Their final products are a glimpse into what it would be like to envision the future after being entirely cut off from the present for almost 70 years. (Photo by Nick Bonner/Kyle Vanhemert/Venice Architecture Biennale)

“Mr Big Dipper”, Nicholas Roemmelt (Denmark). A stargazer observes the constellation of the Big Dipper perfectly aligned with the window of the entrance to a large glacier cave in Engadin, Switzerland. This is a panorama of two pictures, and each is a stack of another two pictures: one for the stars and another one for the foreground, but with no composing or time blending. (Photo by Nicholas Roemmelt/National Maritime Museum/The Guardian)

Tree trunks and rocks are set up to support a leaning wall of Li Yonghua's damaged cave house in an area where land is sinking next to a coal mine, in Helin village of Xiaoyi, China's Shanxi province, August 2, 2016. (Photo by Jason Lee/Reuters)

A Muslim pilgrim makes his way to Hera cave, where Muslims believe Prophet Mohammad received the first words of the Koran through Gabriel, at the top of Mount Al-Noor during the annual haj pilgrimage in the holy city of Mecca, September 21, 2015. (Photo by Ahmad Masood/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.