A worker sprays disinfectant as sanitization operations against Coronavirus are carried out in the museum hosted by the Maschio Angioino medieval castle, in Naples, Italy, Tuesday, March 10, 2020. (Photo by Alessandro Pone/LaPresse via AP Photo)

Firefighters work to put out flames during a wildfire in Sokcho, South Korea, April 5, 2019. South Korea grappled with the massive blaze that roared through forests and cities along the eastern coast, declaring a national emergency and mobilizing all available resources to bring the inferno under control. (Photo by Yonhap via Reuters)

An EF-2 tornado begins to rope out on the outskirts of Mangum, Oklahoma, U.S. on May 20, 2019. Multiple tornadoes touched down and heavy rain flooded areas across Oklahoma. (Photo by Brett Conner/ZUMA Wire)

A firefighter works outside of a building where an explosion and a fire broke out in Shimbashi area of Tokyo on July 3, 2023. (Photo by Yuichi Yamazaki/AFP Photo)

A curious trio of owl monkeys peep out of a tree hollow on the Marañón River near the city of Nauta, Peru in April 2024. (Photo by James Cai/Solent News)

A woman holding a dog walks out of a plane during a press event introducing Bark Air, an airline for dogs, at Republic Airport in East Farmingdale, New York on May 21, 2024. (Photo by Eduardo Munoz/Reuters)

A pair of macaques check themselves out in the rear view mirror of a motorbike in Chandigarh, India in the last decade of August 2024. (Photo by Anuj Jain/Media Drum Images)

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.