A man strikes a pose in front of a giant torta, or sandwich, during a press conference to promote the 13th annual Torta Festival, in Mexico City, Wednesday, July 20, 2016. The five day festival presents a variety of the Mexican street food made from the most exotic ingredients that include ostrich or stingray, to the classic ham, grilled steak or slow cooked pork. The festival's purpose is to maintain the tradition of eating tortas, and promote the vendors of the Mexican sandwich. (Photo by Marco Ugarte/AP Photo)

A driver steers a lorry laden with bags of plastic bottles across a recycling yard at the outskirts of Beijing, China, August 19, 2016. As authorities try to control Beijing's burgeoning population and capitalize on skyrocketing land prices, scrap collectors say they are being pushed out despite playing a vital role in China's unique recycling ecosystem. (Photo by Thomas Peter/Reuters)

A dog from the K9 Division of the Sri Lanka Army’s Commando Regiment performs during an event to mark International Children’s Day at a school in Welisara, Colombo, Sri Lanka, 01 October 2016. Sri Lanka marks the Children's Day on 01 October with more emphasis on prevention of child abuse. (Photo by M.A. Pushpa Kumara/EPA)

A youth in make-up waits for the start of the annual Zombie walk in Mexico City, Saturday, October 22, 2016. Hundreds dressed in rags and ghoulish makeup to look bloody and decaying, gathered in the historic center of Mexico's capital. (Photo by Christian Palma/AP Photo)

A six-year-old acrobat performs on the opening of a tourist festival in Bozhou, Anhui province, China May 3, 2015. (Photo by Reuters/China Daily)

People slide down a 1,082 feet (330 metre) long inflatable water slide in Hong Kong, China August 22, 2015. (Photo by Tyrone Siu/Reuters)

Galapagos – Rocking the Cradle: Four major ocean currents converge along the Galapagos archipelago, creating the conditions for an extraordinary diversity of animal life, April 25, 2016. The islands are home to at least 7,000 flora and fauna species, of which 97 percent of the reptiles, 80 percent of the land birds, 50 percent of the insects and 30 percent of the plants are endemic. (Photo by Thomas P. Peschak for National Geographic/World Press Photo)

American soldiers leaping from an armoured personnel carrier during exercises in Korea, 17th March 1954. (Photo by Three Lions)