A man rides a horse at a playground on a hill in Kabul April 19, 2015. (Photo by Mohammad Ismail/Reuters)

Migrants prepare their food outside shelters in a muddy field called the Grande-Synthe jungle, near Dunkirk, northern France, January 12, 2016. The Grande-Synthe jungle is a camp of tents and makeshift shelters where migrants and asylum seekers from Irak, Kurdistan and Syria gather. (Photo by Benoit Tessier/Reuters)

Boys play with a drainage culvert used for flood control in Las Pinas, Metro Manila February 28, 2016. (Photo by Erik De Castro/Reuters)

Amundsen-Scott South Pole Station experiences months of darkness. The sun dips below the horizon on March 21, after which follows several weeks of twilight before complete darkness results. Photo taken on June 25, 2009. (National Science Foundation/Jeremy Johnson)

Chinese women ride a bicycle together on a street September 10, 2014 in Beijing, China. (Photo by Kevin Frayer/Getty Images)

A soldier stands guard on the aircraft park of the Pyongyang Airport on April 3, 2011 in Pyongyang, North Korea. Pyongyang is the capital city of North Korea and the population is about 2,500,000.