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)

Two girls wearing traditional Sevillian dresses talk during the “Feria de Abril” (April Fair) in Sevilla on April 30, 2017. The fair dates back to 1847 when it was originally organized as a livestock fair but has turned into a week of flamenco dancing, music and bullfighting. (Photo by Cristina Quicler/AFP Photo)

A priest is seen looking out of Abuna Yemata church’s only window. Priests cheerfully tell visitors that pregnant women, babies and old people attend Sunday services and no one has fallen off. (Photo by Ethiopia – The Living Churches of an Ancient Kingdom/The American University in Cairo Press/The Guardian)

The Boeing 747-8 cargo plane pilot has seen thunderstorms, shooting stars and sunsets from up above the clouds and has looked down on mountaintops, carpets of cloud and cities lit up at night. The incredible pictures give a glimpse of the view from the pilots are treated to every day. Here: Shooting stars over India. (Photo by Christiaan van Heijst/Caters News Agency)

Two hippopotamus are fed with pumpkins at the Hanoi Zoo, in Hanoi, Vietnam, 25 October 2018. The zoo has been the home for more than 800 animals of over 90 different species, including three hippopotamus, since it was built in 1976. (Photo by Luong Thai Linh/EPA/EFE)

Jose Zamora, 8, has a dove rubbed over his body during the Afro-Cuban religion Santeria ceremony amid concerns about the spread of the coronavirus disease (COVID-19) outbreak, in Havana, Cuba, March 28, 2020. (Photo by Alexandre Meneghini/Reuters)

People huddle to get on a bus after the government has eased restrictions on public transport amid concerns over the coronavirus disease (COVID-19) outbreak in Dhaka, Bangladesh, June 4, 2020. (Photo by Mohammad Ponir Hossain/Reuters)

A wildlife caregiver holds an orphaned wombat at the Native Wildlife Rescue center on January 29, 2020 in Robertson, Australia. The center has taken in many burned kangaroos and wallabies injured in recent bushfires. Wombat orphans are often rescued from the pouch of their mothers struck by vehicles. (Photo by John Moore/Getty Images)