A boatman rests on his boat in the flooded Ganges river under the Shastri bridge at Daraganj Ghat, in Allahabad, India on August 22, 2019. (Photo by Sanjay Kanojia/AFP Photo)

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 man tries to extinguish an advertisement board set on fire during a demonstration of French labour union members and workers, as France faces its 38th consecutive day of strike against French government's pensions reform plans, in Paris, France on January 11, 2020. (Photo by Gonzalo Fuentes/Reuters)

A brushtail possum whose ears and legs have been burnt from recent bushfires sits in a cage before being transported to a wildlife hospital, in Batemans Bay, South of Sydney, Australia, 14 January 2020. (Photo by Steven Saphore/EPA/EFE)

Children react after what activists said was shelling by forces loyal to Syria's President Bashar al-Assad near the Syrian Arab Red Crescent center in the Douma neighborhood of Damascus May 6, 2015. (Photo by Bassam Khabieh/Reuters)

Faithful wearing face mask pray during the Arafah prayer ceremony ahead of Eid al-Adha, at the Tehran university’s mosque in Tehran, Iran, 30 July 2020. Iran will not hold the Eid al-Adha prayers and ceremonies over the coronavirus (COVID-19) crisis in the country. (Photo by Abedin Taherkenareh/EPA/EFE)

Woman and man playing domination games in bed. (Photo by NDAB Creativity/Rex Features/Shutterstock)

A Kazakh hunter walks with his tamed golden eagle during an annual hunting competition in Chengelsy Gorge, some 150 km (93 miles) east of Almaty February 22, 2013. (Photo by Shamil Zhumatov/Reuters)