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)

The Golden Gai is a sliver of old Tokyo in a modern metropolis filled with endless gleaming buildings. It's a one-of-a-kind tourist attraction, for sure. But it's also a place for a few drinks and friendly chatter among exhausted workers known as “salarymen”. Here: A man strolls through a narrow alleyway clustered with tiny bars and restaurants at the Golden Gai in the Shinjuku district of Tokyo, July 17, 2019. (Photo by Jae C. Hong/AP Photo)

In this September 19, 2019 file photo, an aircraft passes the rising sun during take off at the international airport in Frankfurt, Germany. Germany’s top court has ruled that the government has to set clear goals for reducing greenhouse gas emissions after 2030, arguing that current legislation doesn’t go far enough in curbing climate change. (Photo by Michael Probst/AP Photo/File)

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)

Crews inflate hot air balloons during the 39th annual New Jersey Lottery Festival of Ballooning at Solberg Airport Friday, July 29, 2022, in Readington, N.J. The festival, which runs through Sunday, July 31, will feature as many as 100 balloons. (Photo by Julia Nikhinson/AP Photo)

People attend The Night of Ancient Bonfires event in Saulkrasti, Latvia on August 27, 2022. During The Night of Ancient Bonfires people light bonfires along the coastline of the Baltic Sea. (Photo by Ints Kalnins/Reuters)

Racegoers brave the conditions during 2022 Melbourne Cup Day at Flemington Racecourse on November 1, 2022 in Melbourne, Australia. (Photo by Martin Keep/Getty Images for VRC)

Lord Roscoe the cat runs through the crocuses on the lawns at the National Trust's 17th-century Ham House and Garden in Richmond, London on Monday, March 6, 2023. In recent years more than 500,000 bulbs have been planted to create a spectacle for visitors and to attract bees, butterflies and other pollinating insects. (Photo by Kirsty O'Connor/PA Images via Getty Images)