Crew members work to secure a hot-air balloon after landing at the city of Luxor, south of Cairo, Egypt December 13, 2016. (Photo by Amr Abdallah Dalsh/Reuters)

Željava Air Base, situated on the border between Croatia and Bosnia and Herzegovina under Plješevica Mountain, near the city of Bihać, Bosnia, was the largest underground airport and military air base in the former Yugoslavia, and one of the largest in Europe. (Photo by Thomas Windisch/Exclusivepix Media)

National Geographic has created “Air, Land & Sea: the 50 greatest wildlife photographs” exhibition. Here: CT4 Crocodile cave on the Salamat river. Set up with Nathan Williamson last chip rain came while we were with the nomads. (Photo by Michael Nichols/National Geographic)

This computer image provided Monday March 17, 2014 by the Press Office of socialist candidate to Paris Mayor Anne Hidalgo, shows a tunnel of abandoned railway from the 19th century, now ramshackle and overgrown, turned into a cinema. Hidalgo’s plan envisions not just a green space but in the tunnels, places for farming fish and mushrooms. (Photo by AP Photo/Anne Hidalgo's Press Office)

Model Bella Hadid presents a creation by designers Vivienne Westwood and Andreas Kronthaler as part of their Fall/Winter 2020/21 women's ready-to-wear collection show during Paris Fashion Week in Paris, France on February 29, 2020. (Photo by Piroschka van de Wouw/Reuters)

A model wears a creation for the Balmain Spring/Summer 2019 Haute Couture fashion collection presented in Paris, Wednesday January 23, 2019. (Photo by Thibault Camus/AP Photo)

Models present creations by designer Tommy Hilfiger as part of his Fall/Winter 2019-2020 women's ready-to-wear collection show during the Paris Fashion Week in Paris, France, March 2, 2019. (Photo by Regis Duvignau/Reuters)

Cara Delevingne and other models react while presenting creations by late designer Karl Lagerfeld as part of his Fall/Winter 2019-2020 women's ready-to-wear collection show for fashion house Chanel at the Grand Palais during Paris Fashion Week in Paris, France on March 5, 2019. (Photo by Regis Duvignau/Reuters)