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.

To an outsider, their passion is at times illegal and often on the verge of life and death. But climbing rooftops of high-rise buildings and exploring abandoned facilities is in the blood of these young Muscovites. The small group calls itself “Rudex”, which stands for “roof and decay exploration”, and is akin a Western youth craze known as urbex or “urban exploration” of man-made structures. Here: Urban explorer Vad Him of Rudex team jumps whilst on a rooftop in Moscow, Russia, August 14, 2017. (Photo by Maxim Shemetov/Reuters)

In this January 8, 2015 photo, a monk Kenmyo Muta bows at the condominium construction site and the gate of Sengakuji temple in Tokyo. The “47 ronin” samurai who inspired the long-loved saga of loyalty and honor eulogized in films, books and plays are fighting a new kind of battle in urban Japan. An apartment complex is going up next to the curved tile-roofed Sengakuji temple where the three-century-old graves of the ronin, or masterless samurai, lie. The banner reads: “We only hope to protect landscape of Sengakuji temple”. (Photo by Eugene Hoshiko/AP Photo)

These stunning pictures show a normally vicious tiger calmly swimming in a pool of algae, on Jule 9, 2014. The powerful cat takes a refreshing break by taking a dip in the bright green algae. But it looks like this big cat is scared of getting his head wet as he strains to keep it above the water. After splashing around for a bit the tiger gets out and tries to air-dry with specks of the vegetation dripping off his fur. The striking pictures were taken at Copenhagen zoo by snapper Soren Lundgren Neilson. (Photo by Soren Nielsen/Caters News)

Leanna Arcila, 7, is licked by Watson, a therapy dog with the Pawtucket police department, as she receives her COVID-19 vaccination from Dr. Eugenio Fernandez at Nathanael Greene Elementary School in Pawtucket, R.I., Tuesday, December 7, 2021. Even as the U.S. reaches a COVID-19 milestone of roughly 200 million fully-vaccinated people, infections and hospitalizations are spiking, including in highly-vaccinated pockets of the country like New England. (Photo by David Goldman/AP Photo)

Today is what is known as the equilux and it happens when day and night are equal and occurs a few days before the spring equinox, and a few days after the autumn equinox. What appears to be a floating leaf is actually a stray sticking to a wet car windshield in a park in Scaggsville, Maryland on September 25, 2024. Today sunrise was at 7:02am and sunset took place at 7:02pm. The green and orange colored leaf (about half for each color) seems to represent the transition from Summer to Fall. (Photo by Michael S. Williamson/The Washington Post)

A woman prays during a Sarwan Brata (fast) offering to Lord Shiva, the Hindu god of creation and destruction, at the Pashupatinath Temple in Kathmandu, Nepal, 21 July 2025. Nepalese Hindu women wearing red, yellow and green attire, flock to temples during Sarwan month to pray for a long and prosperous life for their husbands, or to find a good husband. (Photo by Narendra Shrestha/EPA)

The May Queen during the Beltane Fire Festival in Edinburgh, Scotland on April 30, 2022. A dynamic reinterpretation of an ancient Celtic celebration of the return of summer, the festival is centered around the story of the May Queen and the Green Man, and the lighting of the Beltane bonfire, symbolic of purification, healing and new life. Edinburgh's Beltane celebrations are the largest of their kind in the world with around 250 volunteer performers and thousands of spectators. (Photo by Jane Barlow/PA Images via Getty Images)