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)

Visitors outside the venue for Seoul fashion week in Seoul, South Korea on September 3, 2024. (Photo by Lee Jin-man/AP Photo)

Contestants of a tourism beauty pageant balance eggs on their collarbones as they cruise along the Yellow River in Jiyuan, Henan province, China, June 22, 2015. The contestants believe that if they are slim enough, their collarbones will allow them to balance the eggs securely on their bodies. (Photo by Reuters/Stringer)

Revellers cool themselves in the Danube River during the Sziget music festival on an island in Budapest, Hungary August 12, 2015. The event is one of the biggest cultural events of Europe, offering art exhibitions, theatrical and circus performances and music concerts. Almost 200 performers from 47 countries will entertain the hundreds of thousands of visitors from 11 to 18 August. (Photo by Laszlo Balogh/Reuters)

Nubian women sell traditional handicrafts at the Nubian Gharb Suheil village, near Aswan south of Egypt, October 1, 2015. For half a century, Egypt's Nubians have patiently lobbied the government in Cairo for a return to their homelands on the banks of the upper Nile, desperate to reclaim territory their ancestors first cultivated 3,000 years ago. (Photo by Mohamed Abd El Ghany/Reuters)

This September 22, 2014 photo, shows a building with street art murals in the Santurce neighborhood in San Juan, Puerto Rico. (Photo by Ricardo Arduengo/AP Photo)

“Catasta” wearing a latex hexus costume poses in the grounds of St Mary's Church during the “Whitby Goth Weekend”, North Yorkshire, on November 2, 2014. The event grew out of the punk scene in 1984 with its own style of music and fashion. The event in Whitby now attracts Goths from all over Europe and creates over 1 million pounds in revenue for local busnisess. (Photo by Anna Gowthorpe/PA Wire)

Four men dressed as zombies participate in a Zombie Walk procession in the streets of Paris October 12, 2013. (Photo by Benoit Tessier/Reuters)