“Kids of Sapa”. Four little beautiful Hmong girls from Lao Chai Village, near Sapa, Vietnam. (Photo and caption by Felipe Hanower/National Geographic Traveler Photo Contest)

Donald Ganslmeier, operator of the Motodrom, rides a motorbike inside the Motodrom during a press tour at Theresienwiese on the premises of the 182nd annual Oktoberfest in Munich, Germany, September 17, 2015. (Photo by Matthias Balk/EPA)

A girl rides on a train as she takes part in the first edition of the No Pants Subway Ride in Bucharest, Romania, Sunday, January 11, 2015. The No Pants Subway Ride is an annual which was started in 2002 by Improv Everywhere in New York, the goal is for riders to get on the subway train dressed in normal winter clothes without pants and keep a straight face. (Photo by Vadim Ghirda/AP Photo)

Tibetan monks dressed as demons attend the Beating Ghost festival at the Yonghe Temple, also known as the Lama Temple, in Beijing on March 19, 2015. The Beating Ghost festival, or Da Gui festival in Chinese, is an important ritual of Tibetan Buddhism and is believed to expel evil spirits and shake off troubles. (Photo by Wang Zhao/AFP Photo)

A man carrying a sailfish walks through Hamarweyne district in South Mogadishu on March 25, 2015. (Photo by Carl De Souza/AFP Photo)

A German Air Force Officer sits astride a dead boar outside a house where he is stationed near the Western Front, in this 1918 handout picture. This picture is part of a previously unpublished set of World War One (WWI) images from a private collection. The pictures offer an unusual view of varied and contrasting aspects of the conflict, from high tech artillery to mobile pigeon lofts, and from officers partying in their headquarters to the grim reality of life and death in the trenches. The year 2014 marks the centenary of the start of the war. (Photo by Reuters/Archive of Modern Conflict London)

This photo taken on August 7, 2016 shows mahjong enthusiasts playing mahjong under water in a swimming pool at a diving club in the Chinese city of Chongqing. Only participants with proper diving certification were allowed to take part in the underwater competition. (Photo by AFP Photo/Stringer)

A Filipino dancer performs with fire to mark the Chinese Lunar New Year in Manila's Chinatown, Philippines, 28 January 2017. Chinese around the world celebrate the Lunar New Year on 28 January 2017, the first day of the year of rooster. (Photo by Francis R. Malasig/EPA)