Colombia's Harold Tejada climb Plateau des Glieres during the stage 18 of the Tour de France cycling race over 175 kilometers (108.7 miles) from Meribel to La Roche-sur-Foron, France, Thursday, September 17, 2020. (Photo by Thibault Camus/AP Photo)

Yanna Xian, 24, and her boyfriend Mitch Brown, 27, were swimming while on a boat tour off Honolulu, Hawaii last year, when a curious two-week-old humpback approached them. (Photo by South West News Service)

Spectators in costume line the race route during the 12th stage of the 109th edition of the Tour de France cycling race, 165,1 km between Briancon and L'Alpe-d'Huez, in the French Alps, on July 14, 2022. (Photo by Marco Bertorello/AFP Photo)

This photograph taken during a government organised media tour shows people in traditional costume standing in Potala Palace Square as the Potala Palace – classified as a World Heritage Site by Unesco in 1994 – is seen in the background in the regional capital Lhasa, in China's Tibet Autonomous Region, on June 1, 2021. (Photo by Hector Retamal/AFP Photo)

U.S. first lady Melania Trump steps out of her motorcade vehicle as she departs Washington for a tour of several African countries from Joint Base Andrews, Maryland, U.S., October 1, 2018. (Photo by Carlo Allegri/Reuters)

A supporter dressed as flamingo cheers on the riders during the 12th stage of the 102nd Giro d'Italia – Tour of Italy – cycle race, 158kms from Cuneo to Pinerolo on May 23, 2019. (Photo by Marco Bertorello/AFP Photo)

Son doong cave is a cave in Phong Nha-Kẻ Bàng National Park, Bố Trạch district, Quảng Bình Province, Vietnam. Currently the biggest known cave in the world, the cave is located near the Laos-Vietnam border. Inside is a large, fast-flowing underground river.
In early August 2013, the first tourist group explored the cave on a guided tour at a cost of US$3,000 each. The group had six members from Australia, Norway, Russia and USA and spent 7 days and 6 nights for the tour. Next exploration trips will be arranged.

An inmate with a tattoo of Santa Muerte (The Saint of Death) reacts in the Topo Chico prison, during a media tour, in Monterrey, Mexico, February 17, 2016. The director of a prison in northeast Mexico where 49 people died in a riot this week was accused of murder and detained, along with two others, a state prosecutor said on Saturday. (Photo by Daniel Becerril/Reuters)