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)

Students wearing mask hold hands to surround the St. Stephen's Girls' College in Hong Kong, Monday, September 9, 2019. Thousands of demonstrators in Hong Kong urged President Donald Trump to “liberate” the semiautonomous Chinese territory during a peaceful march to the U.S. Consulate on Sunday, but violence broke out later in the business and retail district as police fired tear gas after protesters vandalized subway stations, set fires and blocked traffic. (Photo by Kin Cheung/AP Photo)

“The Reward”. “A spot that a friend and I found that takes a bit of effort to get to. Needs the right swell and wind direction to come together for the backwash to really happen. We had been many times with OK results, but this morning everything lined up perfectly and I was rewarded with this split-second moment in time under some amazing morning light”. (Photo by Scott Harrison/2019 UK Surf Photo of the Year)

A college girl takes part in the Holi festival celebrations in Bhopal, India, 19 March 2019. Holi is celebrated on the full moon day and marks the beginning of the spring season. Holi will be celebrated as the Hindu spring festival of colors across the country on 21 March. (Photo by Sanjeev Gupta/EPA/EFE)

Shepherd brothers Mustafa Erbay and Baran Erbay train their camels on snowy grounds, enabling them to become champions in competitions held in the Aegean and Mediterranean regions in Baskale district of Van, Turkey on February 1, 2020. (Photo by Ozkan Bilgin/Anadolu Agency via Getty Images)

Women walk on a sidewalk in northern Tehran, Iran, Thursday, January 9, 2020. (Photo by Vahid Salemi/AP Photo)

Syrian dancer and choreographer Yara al-Hasbani performs a dance on the empty Trocadero square in front of the Eiffel tower in Paris on April 22, 2020, on the 37th day of a strict lockdown in France to stop the spread of COVID-19 (novel coronavirus). (Photo by Sameer Al-Doumy/AFP Photo)

An exotic dancer wears personal protective equipment while taking a tip in a drive-through go-go dance tent offered by the Lucky Devil Lounge strip club in the wake of the coronavirus disease (COVID-19) restrictions in Portland, Oregon, U.S. April 24, 2020. (Photo by Terray Sylvester/Reuters)