Vietnam’s Son Doong cave, the largest in the world, could hold a 40-story skyscraper inside. The pristine ecosystem has its own river and jungle. Despite its size, Son Doong wasn’t discovered until 1991. It was lost again for nearly two decades and was fully explored for the first time in 2009. (Photo by Jason Speth/HuffPost)

Emma Raducanu of Great Britain takes a selfie after victory over Stephanie Voegele of Switzerland in the first round of the women's singles of the US Open at the USTA Billie Jean King National Tennis Center on August 31, 2021 in New York City. (Photo by Rex Features/Shutterstock)

The 12th round of the 2024 Motocross World Championship got under way in Lombok, Indonesia, on July 07, 2024. Jeffrey Herlings of the Netherlands won the round, and there are eight more to go. (Photo by IPA/Splash News and Pictures/Rex Features/Shutterstock)

Anita Alvarez of the U.S. receives medical attention during the women's solo free final during FINA World Championships at Alfred Hajos Swimming Complex in Budapest, Hungary on June 22, 2022. (Photo by Lisa Leutner/Reuters)

People wait for a subway train to depart Union Square station, in New York City on June 1, 2025. (Photo by Kevin Coombs/Reuters)

More than 400 people stripped off and ran into freezing waters to celebrate the autumn equinox – and raise money for charity at Druridge Bay, Britain, September 25, 2016. It was the largest turnout the North East Skinny Dip has ever seen in its five-year history, and it was also the first time it has ever rained on the morning of the event. Revellers gathered from 5.30am on Sunday at Druridge Bay, in Northumberland, before baring all in the North Sea. (Photo by David Charlton Photography)

Mongolian Chinese performs a traditional Chinese dance in front of the Olympic Rings located near the National Stadium, the main stadium for the 2020 Tokyo Olympic Games in Tokyo, Japan July 29 2021. (Photo by Androniki Christodoulou/Reuters)

2016 Rio Olympics, Rhythmic Gymnastics, Final, Individual All-Around Final, Rotation 1, Rio Olympic Arena, Rio de Janeiro, Brazil on August 20, 2016. Melitina Staniouta (BLR) of Belarus competes using the hoop. (Photo by Ruben Sprich/Reuters)