Cars are parked near Place de la Concorde on March 12, 2014 in Paris, France. Inset: World War I, German airplanes at Place de la Concorde in Paris, wrecked by celebrating crowds on the day of the restoration of Alsace-Lorraine, November 18, 1918. (Photo by Peter Macdiarmid/Getty Images)

Pierre Thivillon (R), director of the zoological park of Saint-Martin-La-Plaine and his wife Eliane look at Digit, an 18-year-old female gorilla, on August 19, 2016, in Saint-Martin-La-Plaine between Lyon and Saint-Etienne, southeastern France. The zoological park of Saint-Martin-La-Plaine is a shelter for beasts seized by the justice. (Photo by Philippe Desmazes/AFP Photo)

People take part in fake festival called “La Boum” organized by an anonymous group of people on Facebook for an April 1 joke at the Bois de la Cambre, in Brussels, Belgium, 01 April 2021. An anonymous group created a Facebook event called “La Boum”, touting an alleged festival to take place with famous DJs as headliners. Thousands of people on social media had shown interest to take part in the gathering, while police have advised that no authorization has been given for a music event. (Photo by Stephanie Lecocq/EPA/EFE)

Fans of Gimnasia de La Plata choke on tear gas during a local tournament match between Gimnasia de La Plata and Boca Juniors in La Plata, Argentina, Thursday, October 6, 2022. The match was suspended after tear gas thrown by the police outside the stadium wafted inside affecting the players as well as fans who fled to the field to avoid its effects. (Photo by Gustavo Garello/AP Photo)

Prince Charles, Prince of Wales (R) and Camilla, Duchess of Cornwall (L) visit Seppeltsfield Winery in Barossa Valley, Australia, 10 November 2015. The royal couple are on a 12-day tour visiting seven regions in New Zealand and three states and one territory in Australia. (Photo by Daniel Kalisz/EPA)

An installation of Canadian artists Caitlind Brown and Wayne Garrett is displayed during the Lumina Light Festival in Cascais September 14, 2014. Lumina Light Festival shows artworks of artists from several countries, which are displayed during a tour around Cascais. (Photo by Rafael Marchante/Reuters)

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.