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 stands on a mountain summit as he looks over the Inntal valley in the western Austrian village of Gnadenwald, Austria on July 18, 2017. (Photo by Dominic Ebenbichler/Reuters)

A cow sits on an empty beach near Barbate, in Cadiz province, south of Spain, Saturday, February 5, 2022. (Photo by Emilio Morenatti/AP Photo)

Players, Sophie Powell, Cara Gainer and Gabriella Cowley and their caddies look on as a fire nears the 10th hole during day three of The Rose Ladies Series on The West Course in the first ever ladies professional event at Wentworth Golf Club on August 07, 2020 in Virginia Water, England. (Photo by Naomi Baker/Getty Images)

A couple take photographs alongside the National Monument on Calton Hill, Edinburgh on Wednesday January 5, 2022, ahead of First Minister Nicola Sturgeon's update to the Scottish Parliament on the Covid-19 situation as the Omicron variant sweeps across the country. (Photo by Jane Barlow/PA Images via Getty Images)

People look at a funnel cloud formed near the beach in Barcelona, Spain, Monday, September 21, 2020. (Photo by Emilio Morenatti/AP Photo)

A person sits in a chair next to the Garzweiler lignite opencast mine at the Luetzerath village near Erkelenz, Germany, Tuesday, January 10, 2023. Environmental activists were locked in a standoff with police this week around the hamlet of Luetzerath that's due to be bulldozed for the expansion of a nearby lignite mine. (Photo by Michael Probst/AP Photo)

People walk along Beachy Head, close to Eastbourne on the south coast of England on April 12, 2020, as life in Britain continues over the Easter break, during the nationwide lockdown to combat the novel coronavirus pandemic. Britain's Prime Minister Boris Johnson was making “very good progress” on Saturday in his recovery in hospital from coronavirus, officials said, as the country's deaths toll from the disease approached the grim milestone of 10,000. (Photo by Ben Stansall/AFP Photo)