High-rise buildings are partly covered by heavy fog at Hong Kong's Victoria Harbour Monday, March 20, 2017. Fog blanketing Hong Kong is common in springtime and may greatly affect shipping and aviation. (Photo by Vincent Yu/AP 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)

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

A model stands in a light backstage after presenting the collection by Russian designer Alena Akhmadullina at The Russian State Library, one of the three national libraries of Russia, the largest library in the country, largest in Europe, in Moscow, Russia, on Wednesday, November 29, 2023. (Photo by Alexander Zemlianichenko/AP Photo)

Children try to walk through a flooded street at Kampung Melayu residential area in Jakarta, December 23, 2014. Torrential rains that have continued in Indonesia in recent days have widened the number of flooded areas that include Jakarta and Bandung, a local newspaper said on Tuesday. (Photo by Reuters/Beawiharta)

Models wait for their turn at an audition for the upcoming Lakme Fashion Week (LFW) Summer/Resort 2017 in Mumbai, India, 14 December 2016. Around 83 national and international models participated in the audition from which five got selected. The LFW Summer/Resort 2017 is scheduled to start from 01 to 05 February 2017. (Photo by Divyakant Solanki/EPA)

An invited guest enjoys a private listening experience of a test unit of the Sennheiser HE 1 sound system, which is expected to retail for about S$77370 ($55000), in a hotel suite during the CanJam headphone and personal audio expo in Singapore February 21, 2016. (Photo by Edgar Su/Reuters)

Thousands of species of amphibians are endangered and hundreds have already disappeared, but in recent years, a team of scientists and conservationists have re-discovered some of these “lost” species and uncovered previously unknown varieties. Here: Miniature glass frog. (Photo by Robin Moore)