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 robot takes part in what is billed as the world's first robot half marathon during the Humanoid Robot Half-Marathon held in Beijing on Saturday, April 19, 2025. (Photo by Ng Han Guan/AP Photo)

Female of pygmy hippopotamus called Malaya from Netherlands in zoo in Dvur Kralove nad Labem, Czech Republic, February 22, 2016. (Photo by David Tanecek/CTK via ZUMA Press)

Pedestrians look at the wreckage of a vehicle lodged in a storm drain on a street in Abidjan on June 19, 2018, in which a man was reportedly found dead after floodwaters receded following an overnight downpour in the city. Fifteen people have died in Abidjan, Ivory Coast' s economic capital, during flooding caused by torrential rain overnight, Interior Minister Sidiki Diakite said. Rain poured down overnight on June 19, causing flash floods up to 2.5 metres (more than eight feet) deep, he said. (Photo by Sia Kambou/AFP Photo)

This undated photo provided by NOAA in May 2018 shows aurora australis near the South Pole Atmospheric Research Observatory in Antarctica. When a hole in the ozone formed over Antarctica, countries around the world in 1987 agreed to phase out several types of ozone-depleting chemicals called chlorofluorocarbons (CFCs). Production was banned, emissions fell and the hole shriveled. But according to a study released on Wednesday, May 16, 2018, scientists say since 2013, there’s more of a banned CFC going into the atmosphere. (Photo by Patrick Cullis/NOAA via AP Photo)

This photograph taken on June 8, 2021 shows a street vendor walking past narrow residential houses, known as “nha ong” in Vietnamese or “tube houses”, in an urban area of Hanoi. (Photo by Manan Vatsyayana/AFP Photo)

Grace Ann Nader, Brooks Nader, Mary Holland Nader and Sarah Jane Nader celebrate their new show “Love Thy Nader” at the top of the Empire State Building in NYC on August 26, 2025. (Photo by Erik Pendzich/Rex Features/Shutterstock)