Sophia Weisberg of Brazil competes on the balance beam during the 53rd Artistic Gymnastics World Championships in Jakarta, Indonesia, October 21, 2025. (Photo by Dita Alangkara/AP Photo)

An attendee dressed as Winnie the Pooh talks with a member of the D.C. Metropolitan Police Department during the annual pre-Halloween High Heel Race in Washington, D.C., U.S., October 28, 2025. (Photo by Nathan Howard/Reuters)

A farmer picks marigold flowers to make garlands to sell for Tihar festival, on the outskirts of Kathmandu, Nepal, Wednesday, October 30, 2024. (Photo by Niranjan Shrestha/AP Photo)

Ocean Rebellion demonstrators perform on the Albert Embankment, on the final day of the MEPC 82 meetings in London, UK on October 2, 2024. (Photo by Victoria Jones/Rex Features/Shutterstock)

An aardvark named Draco eats a pumpkin as part of the upcoming “Halloween” at Prague Zoo, Prague, Czech Republic, on October 31, 2024. (Photo by Eva Korinkova/Reuters)

A Day of the Dead performer is seen in the Paddock during previews ahead of the F1 Grand Prix of Mexico at Autodromo Hermanos Rodriguez on October 24, 2024 in Mexico City, Mexico. (Photo by Mark Thompson/Getty Images)

Sonny Colbrelli of Italy celebrates winning the men's Paris Roubaix, a 258 kilometer (160.3 miles) one-day-race cycling race, at the velodrome in Roubaix, northern France, Sunday, October 3, 2021. (Photo by Vincent Kalut/Pool Photo via 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.