A woman wears roller skates with lights on the bottom at Rich City Skate in Richton Park, Illinois, January 12, 2015. A handful of decades-old skating venues put Chicago at the center of a vibrant African-American subculture of urban roller skate dancing that stretches from Atlanta to Detroit and from Los Angeles to New York. While mainstream roller skating has been on a long decline, a new generation of skaters travel a circuit of rinks around the country to compete and show off their moves. (Photo by Jim Young/Reuters)

A boy rides on a snow wagon towed by a robot dressed as a Teddy bear, which only moves forward by moving its legs, during the Ice and snow carnival at Taoranting park in Beijing February 9, 2015. (Photo by Kim Kyung-Hoon/Reuters)

A Polish Air Force MIG-29 fighter (R) and an Italian Air Force Eurofighter Typhoon fighter patrol over the Baltics during a NATO air policing mission from Zokniai air base near Siauliai, Lithuania February 10, 2015. (Photo by Ints Kalnins/Reuters)

A woman dressed as a cleaning lady laughs during “Weiberfastnacht” (Women's Carnival) in Cologne February 12, 2015. Women's Carnival marks the start of a week of street festivals, the highlight of the event being “Rosenmontag” (Rose Monday), the final day of the carnival where mass processions are held. (Photo by Ina Fassbender/Reuters)

A garbage collector, with his horse and cart, prepares to unload rubbish at the municipal dump in Nezahualcoyotl, on the outskirts of Mexico City, February 18, 2015. Hundreds of horse or donkey-drawn carts will disappear from the streets of a municipality in the state of Mexico, located on the outskirts of Mexico City, and will be replaced by motorized vehicles, local authorities said. (Photo by Henry Romero/Reuters)

Female soldiers of the self-proclaimed Donetsk People's Republic hold flowers backstage during a beauty pageant to mark International Women's Day in Donetsk, March 7, 2015. (Photo by Marko Djurica/Reuters)

Two women jump into a frozen pond as they compete in the Polar Plunge at Frozen Dead Guy Days in Nederland, Colorado March 14, 2015. The winter festival in the small mountain town commemorates the 1994 discovery of the corpse of Bredo Morstol, which is now housed in a shed on dry ice above the town. (Photo by Rick Wilking/Reuters)

Cooked and coloured eggs travel along the production line at the Schrall coloured eggs company in the Austrian Village of Diendorf March 16, 2015. Schrall is one of Austria's biggest Easter and coloured eggs producers and makes between eight and 10 million coloured eggs throughout year. (Photo by Leonhard Foeger/Reuters)