The Y-40 Deep Joy is the worlds deepest pool. Y-40 is projected by Architect Emanuele Boaretto and supported by the “Boaretto Group Hotel and Resort”. The name Y-40 is inspired by mathematical symbols. “Y” is the ordinate axis of the Cartesian system and “–40” means the world's record depth or our pool- that is 40 meters underground. (Photo by Courtesy Y40 Deep Joy)

In this photo taken Tuesday, October 14, 2014, skulls and bones are stacked at the Catacombs in Paris, France. The subterranean tunnels, stretching 2 kilometers (1.24 miles), cradle the bones of some 6 million Parisians from centuries past and once gave refuge to smugglers. The site used to close at 5 p.m., but is now staying open until 8 p.m. The change is mainly aimed at allowing more people to visit and reducing long lines, since it can only hold a limited number of people at a time and visits can't be reserved in advance. (Photo by Francois Mori/AP Photo)

A woman sticks out her tongue as she shops at the Quinta Crespo street market in downtown Caracas, Venezuela, Saturday, January 26, 2019. The country's political showdown moves to the United Nations Saturday where a Security Council meeting called by the United States will pit backers of President Nicolas Maduro against the Trump administration and supporters of the country's self-declared interim leader Juan Guaido. (Photo by Rodrigo Abd/AP Photo)

Children wearing cardboard lion dance masks walk along a street in Beijing on January 13, 2023. China has announced its first overall population decline in recent years amid an aging society and plunging birthrate. (Photo by Mark Schiefelbein/AP Photo)

People are seen through a window as they attend the traditional wedding ceremony of Emir's 7 children in Abuja, Nigeria, December 26, 2020. (Photo by Afolabi Sotunde/Reuters)

Smoke rises during an explosion from an Israeli forces strike in Gaza City, Saturday, November 17, 2012. Israel bombarded the Hamas-ruled Gaza Strip with nearly 200 airstrikes early Saturday, the military said, widening a blistering assault on Gaza rocket operations by militants to include the prime minister's headquarters, a police compound and a vast network of smuggling tunnels. (Photo Hatem Moussa/AP Photo)

Workmen use a crane to winch a large stone head, created by British sculptor Emily Young, into Berkeley Square on February 2, 2012 in London, England. (Photo by Oli Scarff/Getty Images)

Giant panda Mei Xiang discovers a birthday cake meant for her cub Bei Bei (NP) who turns one at the Smithsonian National Zoo in Washington, DC on August 20, 2016. (Photo by Linda Davidson/The Washington Post)