A former paratrooper demonstrates his strength and skills while lifting a chair during the celebrations for the Paratroopers Day at the Central park in the Siberian city of Krasnoyarsk, Russia, August 2, 2015. Paratroopers are an elite unit of the Soviet Army, and everyone in the country recognize their blue berets. (Photo by Ilya Naymushin/Reuters)

The 26th annual National Geographic Traveler Photo Contest is now accepting submissions. Official categories include: “Travel Portraits”, “Outdoor Scenes”, “Sense of Place” and “Spontaneous Moments”. The contest is accepting entries until June 30. Photo: “Forest lights”. Aurora Borealis over the forest of the Pyhae Luosto National Park, Finland. (Photo and caption by Nicholas Roemmelt/National Geographic Traveler Photo Contest)

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)

Brides-to-be participate in the "Running of the Brides" race in a park in Bangkok November 28, 2015. A hundred husbands and wives-to-be wore their wedding dresses and running shoes and competed in an event for a combined prize worth 1 million Thai baht ($27,928), according to the organisers. (Photo by Athit Perawongmetha/Reuters)

A truck lays overturned onto a car following strong winds at a Kurnell industrial park after a rare tornado hit the Sydney suburb December 16, 2015. The tornado hit Sydney on Wednesday with destructive winds above 200 km an hour (125 mph) and cricket ball-sized hail, bringing down trees and power lines, tearing off roofs, overturning vehicles and causing flash flooding. (Photo by Jason Reed/Reuters)

A visitor walks on a giant chalk artwork called “Wasting Time” at the Chalk Urban Arts Festival in Sydney on October 25, 2014. The picture is the biggest 3-D artwork created in Australia by two artists, Leon Keer from Holland and Jenny McCracken from Australia. (Photo by Peter Parks/AFP Photo)