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)

Nikolai Vasilyev, 64, dressed as Father Frost, the Russian equivalent of Santa Claus, water-skis along the Yenisei River outside the Siberian city of Krasnoyarsk, Russia December 19, 2017. Vasilyev, former teacher of the Siberian State Aerospace University, constructed the water skis out of plastic foam and designed the sticks to propel him forward, while travelling on the water surface. (Photo by Ilya Naymushin/Reuters)

One-month-old cubs given birth by giant panda “Su Shan” are seen at Shenshuping giant panda base on August 17, 2021 in Aba Tibetan and Qiang Autonomous Prefecture, Sichuan Province of China. (Photo by He Haiyang/VCG via Getty Images)

A motorway bridge crosses the icy Hunhe River in Shenyang, China on December 12, 2019. (Photo by Costfoto/Barcroft Media)

A cat wearing a dress is carried around in a transparent rucksack at the annual Pet Expo Thailand 2021 in Bangkok on November 25, 2021. (Photo by Jack Taylor/AFP Photo)

Locals dress up as Mazcaras to celebrate Entroido on February 21, 2023 in A Xironda, Spain. Entroido is an ancient rural carnival celebrated in Galicia during the previous days of Ash Wednesday. Each town has its traditional characters and costumes. In the small village of A Xironda, locals dress up as Mazcaras with their characteristic masks, cowbells at the waist and whips, and then run through the streets. (Photo by Brais Seara Fernandez/Getty Images)