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 Bosnian special forces soldier returns fire 06 April 1992 downtown Sarajevo as he and civilians come under fire from Serbian snipers. The Serb extremists were shooting from the roof of a hotel at a peace demonstration of some of 30,000 people as fighting between Bosnian and Serb fighters escalated in the capital of Bosnia- Hercegovina. (Photo by Mike Persson/AFP 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)

Beautiful red sunset sky over Edinburgh, Scotland. Edinburgh is the capital city of Scotland and a popular tourist destination. It is also a major European financial (fund management) centre. Prominent buildings from left to right are: Edinburgh Castle, The Balmoral Hotel Clock Tower and The Scott Monument. (Photo by John Lawson/Getty Images)

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)

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 flock of Adjutants storks sit on a garbage dump at Borgaon in Guwahati, Assam, India, 17 October 2019. Wildlife activists and environmentalists have protested in the past for shifting the garbage dump to another site since it is situated near the Deepor Beel Bird Sanctuary. (Photo by EPA/EFE/Stringer)

Boeing 747-400 of KLM in approach for the “Princess Juliana” airport, Netherlands Antilles Sint Maarten on July 2, 2002. (Photo by LUPOO/Ullstein Bild via Getty Images)