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 man driving a vintage car reacts as he passes by crabs crossing a highway on their way to spawn in the sea in Playa Giron, Cuba on April 25, 2017. Each year, after the first spring rains, millions of red, yellow and black landcrabs march for days from the surrounding forests to the bay on Cuba's southern coast to spawn in the sea. (Photo by Alexandre Meneghini/Reuters)

Icelandic horses walk in their paddock at a stud farm in Wehrheim near Frankfurt, Germany, as the sun rises Tuesday, June 1, 2021. (Photo by Michael Probst/AP Photo)

An Iranian girl walks at the Tochal ski resort, in north of Tehran, Iran on December 12, 2019. (Photo by Nazanin Tabatabaee/WANA via Reuters)

American rapper Saweetie and Quavo seen leaving Boa Steakhouse in West Hollywood, CA. on July 19, 2020. The couple appeared to enjoy dinner and posted a pda filled Instagram story at the restaurant. Saweetie and Quavo looked stylish as they made their way to their car. (Photo by Backgrid USA)

Participants of the “Lady in red“ procession, marking the day of the Summer Solstice, walk on a promenade of the Yenisei River in Krasnoyarsk, Russia on June 22, 2019. (Photo by Ilya Naymushin/Reuters)

A man walks on a slackline during the 7th edition of the European “Marmotte Highline Project” (MHP) festival in Lans-en-Vercors, near Grenoble, eastern France, on July 4, 2019. The event, during which the participants will be able to evolve on the various highlines located in the Regional Natural Park of Vercors, takes place until July 7, 2019. (Photo by Philippe Desmazes/AFP Photo)

A Dongria tribe girl holds her traditional weapon and dance on the last day of their two days long Niyamraja Festival atop of the Niyamgiri hills near Lanjigarh in Kalahandi district, Orissa state. (Photo by Biswaranjan Rout/AP Photo)