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)

An attendee dances at the start of the “Big Goth Dance Party” during the Porcupine Freedom Festival, or PorcFest, the Free State Project's annual summer gathering in Lancaster, NH on Wednesday, June 25, 2014. (Photo by Matthew Cavanaugh/The Washington Post)

A resident looks at a parade marking the 496th anniversary of Panama City, Panama August 15, 2015. Modern-day Panama City includes the historical ruins of the original Panama Viejo settlement founded on August 15, 1519 by Spaniard Pedro Arias Davila, according to local media. (Photo by Carlos Jasso/Reuters)

Mini-pigs perform during the presentation in Balashikha, Russia on December 19, 2018. (Photo by Maxim Shemetov/Reuters)

A paramedic enters an ambulance vehicle as she responds to a call received by Ambulance Station No 3 of Rostov-on-Don's Emergency Care Hospital on New Year's Day in Rostov-On-Don, Russia on January 1, 2022. (Photo by Erik Romanenko/TASS)

A giant storm cloud can be seen in the sky above swimmers near Mollymook Beach, south of Sydney, March 5, 2014. (Photo by David Gray/Reuters)

Yeshiva School students briefly dance on Grant Street after the menorah lighting outside of the City-County Building for the fifth night of Hanukkah, Thursday, December 26, 2019, in downtown Pittsburgh. (Photo by Alexandra Wimley/Pittsburgh Post-Gazette via AP Photo)

Members of the London School of Samba at the start of the Grand Finale of Notting Hill Carnival in London on August 29, 2022 which has returned to the capital for the first time in three years after being cancelled due to the Covid-19 pandemic. Europe's largest street festival celebrates Caribbean culture and is expected to welcome over 1 million people each day. (Photo by Stephen Chung/Alamy Live News)