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 father crosses a road with his twin daughters in Shanghai, China September 28, 2018. (Photo by Aly Song/Reuters)

Father Christmas reading with three young children. (Photo by Spencer Arnold/Getty Images). Circa 1915

Father Christmas hands out presents to children at the Aid And Adoption Society home at Leytonstone. (Photo by Gerry Cranham/Fox Photos/Getty Images). 7th December 1938

Revelers dressed as Father Frost, the equivalent of Santa Claus, dance during a parade in Almaty December 28, 2014. (Photo by Shamil Zhumatov/Reuters)

A boy sits on his father's shoulders to look at strawberries at the 7th International Strawberry Symposium on February 18, 2012 in Beijing, China. (Photo by Lintao Zhang/Getty Images)

A man and his son ride a horse at Tahrir Square in Sanaa, Yemen on January 21, 2021. (Photo by Khaled Abdullah/Reuters)

This Monday, September 15, 2014 photo shows glazed bricks displayed at the Iraqi National Museum in Baghdad. The Islamic State militants seek to purge society of all influences that don't conform with their strict, puritanical version of Islam. That means destroying not only relics seen as pagan but also Muslim sites they see as contradicting their ideology, particularly Sunni Muslim shrines they see as idolatrous as well as mosques used by Shiites, a branch of Islam they consider heretical. (Photo by Hadi Mizban/AP Photo)