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)

Hindu women worship the Sun god in the polluted waters of the river Yamuna during the Hindu religious festival of Chatth Puja in New Delhi, India, November 3, 2019. (Photo by Adnan Abidi/Reuters)

A Parisian dances at the installation Electronica, a unique look at the great classics of 20th century electronic music, played under the vaults at the Collège des Bernardins part of Nuit Blanche, an annual evening festival of culture and art on October 03, 2020 in Paris, France. Scaled down this year because of the Covid-19 pandemic, the festival is split across the left and right banks of the city with many outdoor exhibitions to enable social distancing. (Photo by Kiran Ridley/Getty Images)

New Forest ponies graze as the sun rises over Godshill in the New Forest, Hants on September 18, 2022, on the day before the Queen's state funeral tomorrow. (Photo by Claire Sheppard/Solent News & Photo Agency)

Two ruddy shelducks fly under a double rainbow in Odisha, India in July 2022. These birds are ruddy shelduck, known locally as the Brahminy duck. They have a wingspan of between 43 and 53 inches and stand at a maximum of 28 inches tall. (Photo by Suman Das/Media Drum Images)

Indian tourists walks during heavy snowfall by Dal Lake in Srinagar on January 6, 2017. The sub-zero temperatures has frozen many water bodies in Kashmir and even drinking water taps have frozen at some places. (Photo by Tauseef Mustafa/AFP Photo)

A woman covers her face as a fire burns in the middle of town during an anti-G20 protest on July 7, 2017 in Hamburg, Germany. Authorities are braced for large-scale and disruptive protests as Leaders of the G20 group of nations arrive in Hamburg for the July 7-8 G20 summit. (Photo by Leon Neal/Getty Images)

Female members of the Chinese People's Liberation Army (PLA) honour guard stand behind a string to ensure that they are in a straight line before a welcoming ceremony for Russian President Vladimir Putin outside the Great Hall of the People in Beijing, China, June 25, 2016. (Photo by Kim Kyung-Hoon/Reuters)