A visitor jumps for a photograph on the world's highest and longest glass-bottomed bridge above a valley in Zhangjiajie in China's Hunan Province on August 21, 2016. The bridge, which opened to the public on a trial basis on Saturday, spans 430 meters (1,410 feet) and rises about 300 meters (984 feet) above a valley in a scenic zone, making it the world's highest and longest glass-bottomed bridge according to Chinese state media. (Photo by Fred Dufour/AFP Photo)

Allie Labutis wears a painted “Merica” on her thigh during the fifth annual Made in America Music Festival in Philadelphia, Pennsylvania September 3, 2016. (Photo by Mark Makela/Reuters)

Snow covers roofs, streets and the Charles River following a winter blizzard in Boston, Massachusetts January 28, 2015. A powerful blizzard struck Boston and surrounding New England on Tuesday, leaving some 4.5 million people grappling with as much as three feet of snow and coastal flooding. (Photo by Brian Snyder/Reuters)

Musicians of the alphorn band "Holdersberger Alp- Traum- Blaeser" perform their skills on a raft floating on the Elbsee lake near Aitrang, southern Germany, on June 11, 2017. (Photo by Karl-Josef Hildenbrand/AFP Photo/DPA)

Cast members Ryan Hansen, Kristen Bell, and Jason Dohring (L-R) pose at the premiere of “Veronica Mars” in Hollywood, California in this March 12, 2014 file photo. (Photo by Mario Anzuoni/Reuters)

Roof-topping enthusiast Daniel Lau takes a selfie with high-rise buildings down below as he stands on the top of a skyscraper in Hong Kong, China on August 15, 2017. A craze that began in Russia has now taken hold in Hong Kong, one of the world's most vertical cities. Mr Lau said he had been inspired by Russian climbers and that he was unafraid of the vertiginous heights he scales. (Photo by ImagineChina/Rex Features/Shutterstock)

Carved pumpkins designed by US pumpkin artist Ray Villafane are pictured during a pumpkin exhibition in Ludwigsburg, southern Germany, on September 8, 2017. (Photo by Sebastian Gollnow/AFP Photo/DPA)

General Maurice Gamelin, General Officer commanding the French Armies, is on a four day visit to England. He went to the staff college at Minley and is seen inspecting an anti-tank gun at Aldershot, on June 7, 1939. (Photo by AP Photo)