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)

The Northern Lights glow green in a spectacular light show above a field of trees frozen solid with snow. (Photo by Jaak Sarv/Solent News & Photo Agency)

Six new Canadians take their oath of citizenship while harnessed on the CN Tower's “Edgewalk” 356 metres (1,168 feet) above Toronto, Ontario, Canada in a still image from video October 9, 2018. (Photo by CN Tower/Handout via Reuters)

A mural signed by “TV Boy” and depicting Pope Francis and U.S. President Donald Trump kissing, is seen on a wall in downtown Rome, Italy on May 11, 2017. (Photo by Tony Gentile/Reuters)

A street entertainer waits for tourists in Havana, Cuba on October 2009. (Photo by Desmond Boylan/Reuters)

Thor Teigen poses in a fur jacket next to a thermometer displaying a temperature of 131 degrees Fahrenheit / 55 degrees Celsius at the Furnace Creek Visitors Center, in Death Valley National Park, Calif., Sunday, July 7, 2024. Forecasters said a heat wave could break previous records across the U.S., including at Death Valley. (Photo by Ty ONeil/AP Photo)

A model wears a creation for Schiaparelli's Haute Couture Spring-Summer 2024 collection presented in Paris, Monday, January 22, 2024. (Photo by Christophe Ena/AP Photo)

A man watches the huge waves which brakes at the Paseo Nuevo's promenade in San Sebastian, Basque Country, Spain on 11 January 2016 where the wind has reached to 90 km/h and have been registred waves of eight kilometres due to the bad weather. (Photo by Juan Herrero/EPA/EFE)