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 so-called “Supermoon” dominates the sky while traffic rolls in the streets in Naypyitaw, Myanmar, 03 December 2017. According to the National Aeronautics and Space Administration (NASA) a series of three “Supermoons” – dubbed the “Supermoon trilogy” – will appear in the sky on 03 December 2017, on 01 January 2018 and and 31 January 2018. A “Supermoon” commonly is a full moon at its closest distance to the earth with the moon appearing larger than usual. (Photo by Hein Htet/EPA/EFE)

A person takes a photo of the skyline with the Shard building in the center, at sunset, from Greenwich Park in London, Tuesday, November 24, 2020. (Photo by Yui Mok/PA Wire via AP Photo)

A person stops to take a picture of the sun setting behind the San Francisco skyline as seen from Grizzly Peak Boulevard in Oakland, Calif., Thursday, Dec. 31, 2020. (Photo by Jose Carlos Fajardo/Bay Area News Group via AP Photo)

An open water swimmer surfaces as she enjoys a socially-distanced dawn swim after breaking the ice on the surface of a lake near Scunthorpe, northern England, January 9, 2021. Faced by a sharp rise in coronavirus infections, driven by the new strain, England entered a strict lockdown on January 5, 2021, with schools and non-essential shops closed for at least six weeks after previous measures failed to halt the steep rise in cases. (Photo by Lindsey Parnaby/AFP Photo)

A robot dog is seen before the Gujarat Titans versus Delhi Capitals match in the Indian Premier League in Ahmedabad, India on April 19, 2025. (Photo by Amit Dave/Reuters)

A girl goes to school just before sunrise in Frankfurt, Germany, Wednesday, December 11, 2019. (Photo by Michael Probst/AP Photo)

Surfers take to the waves at Bondi Beach on October 16, 2021 in Sydney, Australia. COVID-19 restrictions eased across NSW on Monday 11 October for fully vaccinated residents after the state passed its 70 per cent double vaccination target. (Photo by Brook Mitchell/Getty Images)