In this November 2, 2017 photo, Mathew Fulkerson and his wife Leigh Ann pose at their Subterra Airbnb located in a former underground missile silo base near Eskridge, Kan. It was designed to house a nuclear warhead six decades ago – but now, this Cold War silo is the perfect spot for a mini break at just $133 a night. (Photo by Thad Allton/The Topeka Capital-Journal via AP Photo)

A tourist stands in front of Italy's Mount Etna as it spews lava during an eruption on the southern island of Sicily, Italy on March 1, 2017. (Photo by Antonio Parrinello/Reuters)

Gray whale feeding at the surface and showing it's baleen. (Photo by Christopher Swann/Biosphoto)

In this photograph taken on July 7, 2018, an Indian Buddhist monk plays with the wind amongst prayer flags on a hill overlooking Tnagyud Gompa monastery in Komik in Spiti Valley in the northern state of Himachal Pradesh. (Photo by Xavier Galiana/AFP Photo)

“Maya” girl Ines de la Paloma, 9, (L), sits with her friend Nuria Sanchez Caballero, 6, at an altar during “Las Mayas” festivity in Madrid, Spain, May 8, 2016. “Las Mayas” festival is held annually at the beginning of May to celebrate the awakening of nature in Spring. Young girls are chosen to become “Mayas” and sit at altars decorated with flowers so that people can admire them. (Photo by Susana Vera/Reuters)

Festival-goers enjoy on Shipyard Island, the venue of the 24th Sziget (Island) Festival in Northern Budapest, Hungary, 12 August 2016. The festival is one of the biggest cultural events of Europe presenting art exhibitions, theatrical and circus performances and music concerts. (Photo by Polyák Attila/Origo.hu)

A pilgrim prays at Mount Al-Noor, where Muslims believe Prophet Mohammad received the first words of the Koran through Gabriel in the Hera cave, ahead of the annual haj pilgrimage in the holy city of Mecca, Saudi Arabia September 7, 2016. (Photo by Ahmed Jadallah/Reuters)

An anti-coup protester holds a Burkinabe flag in Ouagadougou, Burkina Faso, September 18, 2015. Security forces in the capital of Burkina Faso fired in the air on Friday to disperse demonstrators who burned tyres and blocked neighborhood streets to protest at a military coup this week that derailed a democratic transition. The head of a military junta in Burkina Faso which took power on Thursday has freed interim President Michel Kafando and two of his ministers, state television said on Friday. (Photo by Joe Penney/Reuters)