A child prays next to a woman during Eid al-Fitr prayers in Bucharest, Romania, Monday, May 2, 2022. Members of the Romanian Muslim community gathered for Eid al-Fitr prayers, marking the end of the holy fasting month of Ramadan, at the Dinamo stadium in the Romanian capital, in the largest Muslim public gathering of the year in Romania. (Photo by Andreea Alexandru/AP Photo)

Spurt, an Australian Shepherd performs a obstacle run during Wild Wild Woof A SuperDogs Country & Western Spectacle at the 2025 K-Days Festival in Edmonton, Alberta, Canada, on July 26, 2025. With fast-paced races, gold-prospecting stunts, and plenty of tail-wagging charm, the SuperDogs deliver a high-energy country show the whole family can cheer for. (Photo by Artur Widak/Anadolu via Getty Images)

A woman leaves sauna during the sauna marathon in Otepaa, Estonia on February 2, 2019. Participants have to track down, locate and visit designated saunas in the Otepaa area as fast as possible during the event. The team that completed all of the saunas in the shortest time wins. (Photo by Ints Kalnins/Reuters)

A woman offers a prayer at Pashupatinath Temple during the Teej festival in Kathmandu, Nepal September 4, 2016. During this festival, married Hindu women observe day-long fast and pray for a happy married life while those unmarried pray for a good husband. (Photo by Navesh Chitrakar/Reuters)

Hindu women worship the Sun god Surya in the polluted waters of the river Yamuna during the Hindu religious festival of Chatt Puja in New Delhi October 30, 2014. Hindu women fast for the whole day for the betterment of their family and the society during the festival. (Photo by Ahmad Masood/Reuters)

People wait in beds during the The World's Biggest Breakfast in Bed Guinness World Record Attempt at Martin Place on March 2, 2012 in Sydney, Australia. 289 Australians join forces to create history as Martin Place is transformed into a giant bedroom. All participants was enjoy a substantial breakfast served in bed by celebrity chef “Fast” Ed Halmagyi and a free goodie bag valued at over $100. (Photo by Ryan Pierse/Getty Images)

People enjoy a bath in hot kvass, a traditional fermented beverage made from rye bread, during the sauna marathon near Otepaa, Estonia, February 6, 2016. Participants have to track down and visit the given saunas in the Otepaa area as fast as possible. (Photo by Ints Kalnins/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.