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 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)

A vendor sleeps as his son waits for customers at their roadside vegetable shop in New Delhi, February 12, 2019. (Photo by Adnan Abidi/Reuters)

Natalia Williams dressed as Corpse Bride Emily and Tony Knight as a Mandalorian, arrive at the Bradford Unleashed Comic-Con, an entertainment and comic book convention in England on March 8, 2020. (Photo by Danny Lawson/PA Images via Getty Images)

Young people jump over a bonfire as they take part in the Ivan Kupala Night celebration, a traditional Slavic holiday, outside the small town of Turov, some 270 km south of Minsk, on July 6, 2016. People celebrate Kupala Night with bonfires that last throughout the night with some leaping over the flames as it is believed that the act of jumping over the bonfire cleanses people of illness and bad luck. (Photo by Sergei Gapon/AFP Photo)

“DC3 Wreck”. A capture of a US military DC3 plane wreck at the southern black beach in Iceland. Photo location: Iceland. (Photo and caption by Naian Feng/National Geographic Photo Contest)