A girl attends Friday prayers in front of an army tank in Tahrir Square in Cairo February 18, 2011. Five years ago thousands of protesters took to the streets demanding the end of the 30-year reign of President Mubarak as Egypt became the second country to join the Arab Spring. After weeks of clashes, strikes and protests across Egypt, Mubarak resigned on February 11, 2011. (Photo by Suhaib Salem/Reuters)

Monsoon thunderstorm in Sierra Vista, Arizona. 9 Sept, 2011. (Photo by Steven Maguire)

Penny Farthing cyclists ride near Tower Bridge on June 9, 2011 in London, England. The riders have cycled from Paris ahead of the IG Markets London Nocturne cycling event on June 11, 2011. (Photo by Peter Macdiarmid/Getty Images)

“Unexpected x2 (a.k.a. “how much is that doggie in the window”)”. Taiwan, 2011. (Photo and caption by Asian (Street) Impressions)

A model poses for a portrait backstage during Dakar Fashion Week July 10, 2011. (Photo by Finbarr O'Reilly/Reuters)

Nekama, a baby North Chinese leopard, emerges from a basket at her official presentation to the media at Tierpark zoo on March 15, 2011 in Berlin, Germany. Nekama was born on January 7, 2011 and currently weighs 4.5 kg.