Labourers who work nearby nap on a road as cars drive past in Chongqing Municipality, July 23, 2013. (Photo by Reuters/Stringer)

Mounted cop in action on Tremont Street in Boston, Massachusetts, 1920 – 1929 (approximate). (Photo by Leslie Jones)

King George V inspects the day's kill after a tiger hunt in India during his royal visit to celebrate his accession to the throne. (Photo by Hulton Archive/Getty Images). 1911

Catherine, Duchess of Cambridge speaks to soldiers as she arrives at Calgary Airport on July 7, 2011 in Calgary, Canada. (Photo by Chris Jackson/Getty Images)

Pupils participate in a calligraphy contest to celebrate the New Year in Tokyo January 5, 2016. Over 3,000 calligraphers who qualified in competitions throughout Japan wrote resolutions or wishes onto paper sheets during the annual contest that marks the start of the new year, according to organizers. (Photo by Thomas Peter/Reuters)

A model walks the runway during the Versace show as part of Paris Fashion Week Haute Couture Spring/Summer 2015 on January 25, 2015 in Paris, France. (Photo by Pascal Le Segretain/Getty Images)

This July 2014 image provided by the Bureau of Land Management shows the interior of the Natural Trap Cave in north-central Wyoming. The cave holds the remains of tens of thousands of animals, including many now-extinct species, from the late Pleistocene period tens of thousands of years ago. Scientists have resumed digging for the first time in more than 30 years. (Photo by AP Photo/Bureau of Land Management)

Participants climb over a wall at the “Tough Mudder” endurance event series in Arnsberg September 6, 2014. Competitors who took part in the endurance event saw themselves having to overcome various military style obstacles. (Photo by Ina Fassbender/Reuters)