Members of Japan's idol group “Virtual Currency Girls” wearing cryptocurrency-themed masks perform in their debut stage in Tokyo, Japan, January 12, 2018. Japanese female idols have teamed up to form the ‘Virtual Currency Girls’ group to promote the knowledge of cryptocurrencies through entertainment. Each of its 8 members represents a cryptocurrency: bitcoin cash, bitcoin, ether, neo, nem, ripple, mona, and cardano. (Photo by Kim Kyung-Hoon/Reuters)

Men who are part of a neighbourhood vigilante group hold a hammer and machetes while posing for a photograph after suspected gang leader Makandal was killed and set on fire, amid an escalation in gang violence, in Port-au-Prince, Haiti on March 20, 2024. (Photo by Ralph Tedy Erol/Reuters)

This jaw-dropping footage shows one brave diver getting up close and personal with a group of sharks as he feeds them a long-awaited meal. Ken Kiefer from Houston, Texas captured his friend, Jake, reaching right into the mouth of a hammerhead. (Photo by Ken Kiefer/Caters News Agency)

This handout picture released by the Israeli army on May 31, 2024 shows Israeli soldiers during operations in the Gaza Strip amid the ongoing conflict between Israel and the Palestinian militant group Hamas. (Photo by Israeli Army/AFP Photo)

People watch as a young Palestinian performs an acrobatic jump on the beach, during soaring summer temperatures in Gaza City on June 14, 2024, amid the ongoing conflict between Israel and the Palestinian Hamas militant group. (Photo by Omar Al-Qattaa/AFP Photo)

An English soccer fan kicks a ball as he gather with other fans ahead of a Group C match between England and Slovenia at the Euro 2024 soccer tournament in the city center in Cologne, Germany, Tuesday, June 25, 2024. (Photo by Markus Schreiber/AP Photo)

A cricket is seen posing on an advertising billboard during the Concacaf Nations League group stage football match between Costa Rica and Guadeloupe at the National Stadium in San Jose on September 5, 2024. (Photo by Ezequiel Becerra/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.