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)

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Napoli fans celebrate after winning the Coppa Italia final against Juventus FC, in central Naples, Italy on June 17, 2020. Napoli won the Italian Cup with a 4-2 penalty shootout victory over Juventus following a 0-0 draw in a match played at the Rome Olympic Stadium. (Photo by Salvatore Laporta/IPA/Rex Features/Shutterstock)

An Iraqi man comforts his 4-year-old son at a regroupment center for POWs of the 101st Airborne Division near An Najaf, Iraq, March 31, 2003. The man was seized in An Najaf with his son and the U.S. military did not want to separate them. (Photo by Jean-Marc Bouju/Associated Press)

A woman and her son hold firecrackers during Diwali, the Hindu festival of lights, in Mumbai, India, November 4, 2021. (Photo by Francis Mascarenhas/Reuters)

A man and his son ride a horse at Tahrir Square in Sanaa, Yemen on January 21, 2021. (Photo by Khaled Abdullah/Reuters)