People walk on a sightseeing platform in Zhangjiajie, Hunan Province, China, August 1, 2016. China has opened a 100-metre-long glass skywalk stretching around a cliff on the side of the Tianmen Mountain. The skywalk provides a view of a 300-metre drop and overlooks Tongtian Avenue, a mountain road with 99 turns that snakes up the mountain. When translated in English, it means “Avenue to the Sky”. (Photo by Reuters/Stringer)

A British Army Rolls Royce armoured car outside the Royal Ulster Constabulary police station on York Street in Belfast following riots after an Orange Order parade. (Photo by Fox Photos/Getty Images). 20th June 1935

Far from the fancy throngs who gather at the Pebble Beach Concours d'Elegance every year, another collection of car enthusiasts strive to cough up the worst cars imaginable. The Concours d'Lemons gathers the Edsels, Yugos and Azteks of yesteryear to give the freaky and foul their day in the sun. Photo: The 1973 Electra-King three-wheeler, the dead evolutionary branch of today's electric cars. (Photo by Robert Kerian/Yahoo Autos)

Joseph Szabo was a frustrated high-school teacher in need of inspiration – so he started photographing his students, and captured all the angst and excitement of being caught between childhood and adulthood. Here: “Priscilla”, 1969. (Photo by Joseph Szabo/Courtesy of Michael Hoppen Gallery/The Guardian)

An elephant enjoys its back being scrubbed by the keeper on March 1, 1950. (Photo by Fox Photos/Getty Images)

After finding the bricklaying business too full of ups and downs, this amazing young girl decided to take a shot at iron girdering for a change. She is Miss “Collie” Collier, a reporter for the Chicago Herald-Examiner. August 17, 1920. (Photo by Bettmann Archive/Getty Images)

French tennis champion Suzanne Lenglen (1899–1938) high-kicking during a doubles match at the Wimbledon Lawn Tennis Championships. (Photo by Kirby/Topical Press/Getty Images). 1924

A pro-Russian rebel guards a captured former Ukrainian Army checkpoint outside Vuhlehirsk, Donetsk region, eastern Ukraine, Thursday, February 5, 2015. The rebels have closed in around the town in a strategy they triumphantly refer to as the Debaltseve cauldron. Separatists recently burst through government lines in the rural settlement of Vuhlehirsk. (Photo by Vadim Braydov/AP Photo)