Hannah Rice, 18, jumps from a stump after posing for a photograph next to a large bust of President Franklin D. Roosevelt while touring busts of U.S. presidents in Williamsburg, Va. on March 30, 2019. The statues were once part of an attraction called Presidents Park, which has since closed. (Photo by Matt McClain/The Washington Post)

A mother and her daughter paddle during a Stand Up Paddle (SUP) race of the Alpine Lakes Tour, on Europe's biggest underground lake, in St-Leonard, Switzerland, March 10, 2018. SUP is an offshoot of surfing that originated in Hawaii. Unlike traditional surfing where the rider sits until a wave comes, stand up paddle boarders stand on their boards and use a paddle to propel themselves through the water. (Photo by Denis Balibouse/Reuters)

France's Juliette Ducordeau (Front R) and fellow athletes react after crossing the finish line of the Women's Mass Start 10 km Free event at the FIS Tour de Ski stage on January 8, 2023 in Val di Fiemme. (Photo by Marco Bertorello/AFP Photo)

Children wearing bear fur costumes dance during a parade in Comanesti, Romania, Friday, December 30, 2022. In pre-Christian rural traditions, dancers wearing colored costumes or animal furs, toured from house to house in villages singing and dancing to ward off evil. (Photo by Vadim Ghirda/AP Photo)

American singer-songwriter Taylor Swift speaks to a kid onstage during “Taylor Swift | The Eras Tour” at Johan Cruijff Arena on July 04, 2024 in Amsterdam, Netherlands. (Photo by Carlos Alvarez/Getty Images for TAS Rights Management)

The rising sun is framed between the lighthouses at the end of the pier in Whitby on the Yorkshire coast on March 18, 2025. (Photo by Andrew McCaren/London News Pictures)

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.