Kansas City Chiefs tight end Travis Kelce and Taylor Swift kiss after the AFC Championship NFL football game against the Buffalo Bills, Sunday, January 26, 2025, in Kansas City, Mo. (Photo by Ashley Landis/AP Photo)

Revellers gather for the start of the Annual SantaCon Bar Crawl at Father Duffy Square, a section of Times Square, on December 14, 2019, in New York City. SantCon is an event where people make donations to charitable causes and dress up as a Christmas character and visit bars around the city. (Photo by Steven Ferdman/Getty Images)

Manchester City's Phil Foden celebrates after scoring his side's sixth goal during the Champions League round of 16 second leg, soccer match between Manchester City and Schalke 04 at Etihad stadium in Manchester, England, Tuesday, March 12, 2019. (Photo by Dave Thompson/AP Photo)

New Orleans Saints linebacker Willie Gay Jr. signs autographs for a young fan before the start of an NFL football game against the Kansas City Chiefs Monday, October 7, 2024, in Kansas City, Mo. (Photo by Ed Zurga/AP Photo)

Revellers of street parties known as blocos, dance during a protest against restrictions by city officials in Rio de Janeiro, Brazil, Wednesday, April 13, 2022. City Hall has banned the street parties during Carnival celebrations, which were delayed by almost two months due to the pandemic. (Photo by Silvia Izquierdo/AP Photo)

An activist blocks a highway during a protest demanding the immediate release of hostages held by Hamas and calling for the Israeli government to reverse its decision to take over Gaza City and other areas in the Gaza Strip, near the city of Lod, Israel, Tuesday, August 26, 2025. (Photo by Ohad Zwigenberg/AP Photo)

American singer-songwriter Taylor Swift kisses Kansas City Chiefs tight end Travis Kelce after an AFC Championship NFL football game against the Baltimore Ravens, Sunday, January 28, 2024, in Baltimore. The Kansas City Chiefs won 17-10. (Photo by Julio Cortez/AP 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.