This photographer is walking on thin ice after taking stunning photographs inside an Alaskan ice cave that could collapse at any moment. With it's dazzling turquoise walls and and huge open spaces, it's hard to imagine that this incredible frozen cavern was only formed at the beginning of 2012. But despite it's seemingly mystical allure, the fascinating natural phenomena is at risk of collapsing in on itself without warning. (Photo by Ron Gile/Caters News)

In this picture taken on September 5, 2023, students practice contortionism at the Flower Studio in Ulaanbaatar. Mongolian circus performers fly through the air of a cavernous hall inspectors have warned could collapse at any time, one of the few places left to train if they hope to travel the world with their country's spectacular big top shows. (Photo by Pedro Pardo/AFP Photo)

In this photo taken on Saturday, April 29, 2017, a candle is lit in a roadside shrine as the sun sets across a nearby lake of Pineia in the village of Souli, in the Peloponnese region of southern Greece. Made of iron sheeting, stone, wood, concrete or marble, tens of thousands of such shrines punctuate Greece’s roadside scenery, a common sight in a country that has one of the European Union’s worst road fatality rates. (Photo by Petros Giannakouris/AP Photo)

A single object, a single shape, a single colour,' is how Anish Kapoor summed up Leviathan, his response to the Monumenta challenge this year. Radically departing from Christian Boltanski’s busy collage-like approach in Personnes for Monumenta 2010, Kapoor has filled the 13,500 square metre space with a single cavernous entity which surges through the Grand Palais roof.

Thai military officers dressed in traditional orange monk robes arrive to attend their official ordination ceremony on July 13, 2011 at the Benchamabopit temple, also known as Marble temple, in Bangkok, Thailand. Eighty four of the military officers were ordinated into the Buddhist community over two days, taking leave of absence from their jobs in the Army for three months during the Buddhist lent period. July 16 will mark the first day of the yearly three-month retreat of Buddhist monks where they will practice meditation in temples and study dharma. (Photo by Paula Bronstein /Getty Images)

Children play marbles on the dirt in Garut, West Java, Indonesia on October 17, 2025. This traditional game, which was popular in the 1980s, is now rarely played by children due to the increasing popularity of modern games with advanced technology. According to a survey by the Indonesian Child Protection Commission (KPAI), more than 71.3% of school-age children own gadgets and play them for a considerable amount of time each day, and as many as 79% of child respondents are allowed to play gadgets for purposes other than learning. (Photo by Algi Febri Sugita/ZUMA Press Wire/Rex Features/Shutterstock)

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.