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)

A B-52 bomber is watched by a group of curious onlookers as it lands at RAF Fairford, February 21, 1999. The B52s arrived from the U.S.A. as part of NATO's preparations for air attacks on Yugoslavia as tensions in the Kosovo crisis increased. (Photo by Dylan Martinez/Reuters)

Members of the “Exit Point” amateur rope-jumping group jump from a 44-metre high (144-ft) waterpipe bridge in the Siberian Taiga area outside Krasnoyarsk, September 13, 2015. Rope-jumping, an extreme sport, involves jumping from a high point using an advanced leverage system combining mountaineering and rope safety equipment. (Photo by Ilya Naymushin/Reuters)

Models pose in designs from May Quant's collection on a street in London, England, on October 16, 1969. Grania, left, wears the "Shimmy Shimmy," a white rayon dress over matching pants with a shawl. Baba, center, wears "Razzamatazz," a jumpsuit featuring plastic sequins in blue, silver and red on nylon. Linda wears "Muffit," a pink minidress with an old English style floppy mobcap. (Photo by AP Photo)

Children walk amid a mirror installation titled “Sea of Mirrors”, featuring digital images of fish in the ocean during a preview tour the day before the show's public opening at the AquaRio aquarium in Rio de Janeiro, Brazil, Wednesday, June 14, 2023. (Photo by Silvia Izquierdo/AP Photo)

Jockeys and their horses reflect in the water of Laytown Beach during the third race of the day at the Laytown Races in Co Meath, Ireland on Tuesday, September 12, 2023. (Photo by Clodagh Kilcoyne/Reuters)

Members of Brighton Swimming Club brave the early morning temperature to take a dip in the sea east of the pier on January 5, 2022. The club, founded in 1860, is the oldest in England. (Photo by Simon Dack/Alamy Live News)

Elizabeth Nicolaou, a final year student with the Royal Academy of Dance, strikes a pose on April 28, 2022 near the Cutty Sark ship in Greenwich, London ahead of International Dance Day. First celebrated in 1982, International Dance Day has taken place every year since in anniversary celebration of the birth of Jean-Georges Noverre (1727-1810), considered the creator of modern ballet. (Photo by Guy Corbishley/Alamy Live News)