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 workman sweeping the highest sidewalk in the world, the 81st story of the Empire State Building, the world's tallest building, to the top of which the greatest dirigible “Los Angeles” will attempt to moor, New York, New York, early 1930s. This photo was made 1,248 feet above street level. (Photo by Adam Glickman/Underwood Archives/Getty Images)

An actor holds a fake baby while waiting for the Wintershall Nativity play dress rehearsal to begin at Wintersall Estate on December 12, 2021 in Guildford, England. The Nativity play, which tells the story of the birth of Jesus Christ, has been performed annually since 1990 over the Christmas period by the Wintershall players. (Photo by Hollie Adams/Getty Images)

Visitors visit the upside-down family size house in Taipei, Taiwan, 23 February 2016. The three story upside-down family size house attracts hundreds of visitor’s who are amused with the exhibit. According to the organizers, the total cost of the construction is around 600,000 US Dollars and took 2 months to complete. (Photo by Ritchie B. Tongo/EPA)

A Bangladeshi girl watches from a nearby building after a five-story building was raided by police in Dhaka, Bangladesh, Tuesday, July 26, 2016. Police in Bangladesh's capital raided a five-story building Tuesday that was used as a den by suspected Islamic militants, killing nine of them, the country's police chief said. Police said they belonged to a Bangladeshi group blamed for an attack on a Dhaka cafe earlier this month in which 20 hostages, mostly foreigners, were killed and had been planning another large-scale assault. (Photo by AP Photo)

A man invades the Red Carpet and is held by security at the “How To Train Your Dragon 2” Premiere at the 67th Annual Cannes Film Festival on May 16, 2014 in Cannes, France. The man stuck his head up America`s skirt before being dragged away by security. Pictured: Djimon Hounsou, Cate Blanchett, America Ferrera and Kit Harington. (Photo by Camilla Morandi/IPA)

Amateur astronomer Bill Snyder has been involved with astrophotography since 2007. Photo: The Cygnus Wall is in the southern area of NGC7000 also known as the North America Nebula. It is approximately 1800 light years from Earth, and is in the constellation Cygnus. The Wall is an energized shock front and contains the most concentrated star formations in the nebula. The size of the North America Nebula is about 4 full moons. (Photo and caption by Bill Snyder)

A girl walks to a synagogue of the Tzanz Hasidic dynasty community to read the Book of Esther, which tells the story of the Jewish festival of Purim, in Netanya, Israel, Wednesday, March 23, 2016. The Jewish holiday of Purim commemorates the Jews' salvation from genocide in ancient Persia, as recounted in the Book of Esther. (Photo by Ariel Schalit/AP Photo)