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)

Gray whale feeding at the surface and showing it's baleen. (Photo by Christopher Swann/Biosphoto)

The winner of the Miss Tattoo Brazil 2014 contest, Bruna Barros, shows a tattoo that says 'My body, my rules' during Tattoo Week, the largest convention of art in the skin of Latin America, in Sao Paulo, Brazil, 14 July 2017. A tattooed woman beauty pageant, the new trends and techniques of the tattoo world, body piercing and the environment of the art of definitively painting the body, are all due to be addressed during the seventh edition of the “Tattoo Week Sao Paulo“. (Photo by Sebastiao Moreira/EPA)

A bulldog dressed as Marilyn Monroe poses for a photograph during the annual Tompkins Square Halloween Dog Parade in the Manhattan borough of New York City, October 24, 2015. (Photo by Stephanie Keith/Reuters)

Castle rising in the mist on April 14, 2022. Castle Rising is a ruined medieval fortification in the village of Castle Rising, Norfolk, England. It was built soon after 1138 by William d'Aubigny II, who had risen through the ranks of the Anglo-Norman nobility to become the Earl of Arundel. (Photo by Terry Harris/The Times)

A woman controls a ball on Ipanema beach in Rio de Janeiro, Brazil, April 14, 2016. As hundreds of thousands of tourists begin descending on Rio de Janeiro for the Olympics that start August 5, the headlines have focused on the street violence, the Zika virus, the water pollution and the rush to finish venues and transport. But Rio, known by Brazilians as the “Marvelous City”, glistens despite it all. The beach is a way of life here. (Photo by Nacho Doce/Reuters)

A chimp motions for Santa to deliver his gift during Lion Country Safari's annual Christmas with the Chimps on Thursday, December 20, 2012. (Photo by Bruce R. Bennett/The Palm Beach Post)

Members of a teenage girl gang convincing an unwilling recruit to join the gang, circa 1955. (Photo by Vecchio/Three Lions)