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 woman jumps with balloons while she poses for a picture at a park in Kiev, Ukraine May 6, 2018. (Photo by Valentyn Ogirenko/Reuters)

A woman takes photos as Mount Agung volcano sends up another plume of smoke, seen from the Kubu subdistrict in Karangasem Regency on Indonesia's resort island of Bali on July 5, 2018. Mount Agung roared to life again on July 2, belching a plume of ash 2,000 metres (6,500 feet) high, as well as temporarily shuttering the airport and grounding hundreds of flights after erupting the week before. (Photo by Sonny Tumbelaka/AFP Photo)

A USGS geologist making observations of the fissure 8 lava channel at sunset is pictured in this July 3, 2018 fisheye lens handout photograph near the Kilauea volcano eruption in Hawaii, U.S. (Photo by USGS/Handout via Reuters)

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)

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)

UK Love Island’s star Maura Higgins, 30, stuns as she poses in revealing outfits in her latest photoshoot with brand Ego in Dubai, United Arab Emirates in April 2021. (Photo by EGO)

Tourists visit the water forest by boat at a wetland park in Yangzhou City, east China's Jiangsu Province, 30 July, 2023. (Photo by Meng Delong/ImagineChina/Imaginechina via AFP Photo)