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)

Steam emerges from a cooling tower of the nuclear power plant Leibstadt near Leibstadt, Switzerland, November 18, 2014. (Photo by Arnd Wiegmann/Reuters)

An ambulance with emergency lights on makes its way through snowfall in Iowa, US on December 21, 2022. (Photo by Joseph Cress/AP Photo)

Tourists play on the “Big” piano inside of the toy store FAO Schwarz on the last day that the store will be open in New York, July 15, 2015. FAO Schwarz will officially close the doors of its flagship Fifth Avenue toy store in New York City on Wednesday night, to the dismay of shoppers charmed by the iconic destination for childhood fun. (Photo by Lucas Jackson/Reuters)

Samurai commiting seppuku (hara-kiri) in Japan, circa 1880. (Photo by adoc-photos/Corbis via Getty Images)

A photo from Madonna’s high school yearbook at her childhood home in Rochester, Michigan, circa 1973. (Photo by Rebel Images/Rex Features/Shutterstock)

Heimana Reynolds of USA in action during a training session prior to the World Skate Park World Championships at the Parque Candido Portin​ari in Sao Paulo, Brazil, 11 September 2019. (Photo by Sebastião Moreira/EPA/EFE)

Penny Verdin displays a sleeping squirrel she helped rescue after it was injured during Hurricane Ida, Saturday, September 4, 2021, in Dulac, La. (Photo by John Locher/AP Photo)