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)

Men push a car stucking in the mud on a motorway in Nimba County, Liberia, 28 July 2019. Most highway roads in the rural parts of the country are unpaved. The government of President George Weah has promised to build roads to connect all big cites of Liberia. (Photo by Ahmed Jallanzo/EPA/EFE)

The Golden Gai is a sliver of old Tokyo in a modern metropolis filled with endless gleaming buildings. It's a one-of-a-kind tourist attraction, for sure. But it's also a place for a few drinks and friendly chatter among exhausted workers known as “salarymen”. Here: A man strolls through a narrow alleyway clustered with tiny bars and restaurants at the Golden Gai in the Shinjuku district of Tokyo, July 17, 2019. (Photo by Jae C. Hong/AP Photo)

Firefighters extinguish a fire in Kampar, Riau province on Indonesia's Sumatra island on August 13, 2019. Indonesian authorities are deploying thousands of extra personnel to prevent a repeat of the 2015 fires, which were the worst for two decades and choked the region in haze for weeks. (Photo by Wahyudi/AFP Photo)

A woman instructs a boy on how to pose for pictures in front of a mural depicting Soviet pilot Valery Chkalov – who took a non-stop flight over the Arctic and landed in the US state of Washington in 1937 – at Chkalovskaya metro station in Moscow on August 14, 2019. (Photo by Yuri Kadobnov/AFP Photo)

A girl jumps to touch cherry blossoms in full bloom in Fussa, outskirts Tokyo, Japan, 05 April 2014. Temperatures being very constant made blossoms to keep full bloom for holiday makers. (Photo by Kimimasa Mayama/EPA)

A participant takes part in the annual Jack In The Green parade involving hundreds of costumed revellers joining a four hour procession culminating in the traditional “slaying” of a Jack character to “unleash the spirit of summer” on the May Day week end, in Hastings, southern Britain, May 2, 2016. (Photo by Toby Melville/Reuters)

A man carries a figurine of Santa Muerte or The Saint of Death during the first prayer of the New Year in Mexico City, Mexico January 1, 2017. Nuestra Señora de la Santa Muerte is a female deity of Mexican folk religion, venerated primarily in Mexico and the Southwestern United States. (Photo by Carlos Jasso/Reuters)