People walk on the “Europabruecke” bridge, the world's longest pedestrian suspension bridge with a length of 494m, after the official inauguration of the construction in Randa, Switzerland, 29 July 2017. The bridge is situated on the Europaweg that connects the villages of Zermatt and Graechen. (Photo by Valentin Flauraud/EPA)

Cows belonging to Samburu tribesmen walk around the carcass of an elephant killed by armed cattle herders in Mugui Conservancy, Kenya February 11, 2017. Kenya has declared the ongoing drought affecting many parts of the country a national disaster, calling for aid to counter the situation which is posing a major risk to people, livestock and wildlife. (Photo by Goran Tomasevic/Reuters)

Paramasivan points to the statue of sun god Surya at a temple outside the Kodaikanal Solar Observatory, India, February 5, 2017. In the early morning darkness, Devendran P. walks up a hill to a solar observatory in India's southern hill town of Kodaikanal, trudging the same path his father and grandfather walked in a century-old family tradition of studying the sun. (Photo by Danish Siddiqui/Reuters)

A male red deer with antlers covered in bracken, walks through undergrowth in Richmond Park in south west London, October 3, 2014. Over 600 red and fallow deer roam in the largest of London's Royal Parks, and have their numbers managed in an annual cull each November and February. (Photo by Toby Melville/Reuters)

Ludivine Sagna walks the runway and wears a chocolate costume made by designer and a chocolate maker during the Fashion Chocolate show at Salon du Chocolat at Parc des Expositions Porte de Versailles in Paris, France, October 28, 2014. (Photo by LAURENTVU/SIPA Press)

Tommy Lindsey holds an enormous maple leaf that he found in Mount Vernon, Wash., October 28, 2013. Lindsey was walking with his family when he picked up the leaf that is more than two feet from stem to tip and more than 21 inches wide. (Photo by Frank Varga/The Skagit Valley Herald)

An Afghan child practices walking with his new prosthesis at the International Committee of the Red Cross (ICRC), orthopedic center on September 10, 2011 in Kabul, Afghanistan. After more than 30 years of war and a decade since the 9/11 attacks in the United States, thousands of Afghans, both military and civilian, continue to pay a heavy price from the conflict. The ICRC center makes prosthetics for amputees and helps them, as well as Afghans with spinal injuries and children with congenital birth defects, to learn to walk. (Photo by John Moore/Getty Images)

A woman walk by South Korean police during a anti-terror exercise on March 9, 2012 in Seoul, South Korea. The drill is part of South Korea's preparation for the upcoming 2012 Seoul Nuclear Security Summit, scheduled for March 26 and 27. Some 50 world leaders, including U.S. President Barack Obama, are expected to attend the summit to discuss how to make the world safe without nuclear weapons. (Photo by Chung Sung-Jun/Getty Images)