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.

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)

A media member looks at a humanoid robot portraying the Qin emperor Qin Shi Huang, during an organised media tour to Robot Mall, a store selling humanoid and other robots, in Beijing, China on August 6, 2025. (Photo by Florence Lo/Reuters)

The interior of the first class cabin of the Boeing 787 Dreamliner is seen during a media tour on February 12, 2012 in Singapore. (Photo by Chris McGrath/Getty Images)

(L-R) Diana Burkot, Maria Alyokhina and Olga Borisova perform at the concert of the anti-cremlin and feminist band p*ssy Riot at Funkhaus Berlin on May 12, 2022. The 33-year-old Alyokhina had only recently fled Russia. Based on the book “Riot Days” by Alyokhina, the “p*ssy Riot Anti-War Tour” presented a performance project consisting of music, theater and video recordings. 19 performances have been announced for the tour. The punk band has been a thorn in the side of the Russian government for years. (Photo by Bernd von Jutrczenka/dpa)

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Girls sit inside an empty classroom as they pose for a photograph during a celebration marking the end of the school year in the town of Douma, eastern Ghouta in Damascus, Syria May 21, 2016. (Photo by Bassam Khabieh/Reuters)

Women demonstrate on International Women's Day as they strike to demand the end to domestic violence and the country's prevailing “macho” culture, in Milan, Italy on March 8, 2023. (Photo by Claudia Greco/Reuters)