South Korean police officers show their martial arts' skills during the official launch ceremony of the 2012 Seoul Nuclear Security Summit on February 15, 2012 in Seoul, South Korea. The Korean National Police Agency launched a security squad, exclusively established for the successful hosting of the 2012 Seoul Nuclear Security Summit. The 2012 Seoul Nuclear Security Summit will be held in Seoul from March 26-27, 2012. (Photo by Chung Sung-Jun/Getty Images)

Recruits who earned a place in the Motivation Platoon struggle through water and muck on their way to becoming a Marine or going into some other line of work, October 7, 1971. (Photo by Eddie Adams/AP Photo)

Following a large air raid by German bombers, local people, coming out of their air raid shelters found a bus standing on end in a large crater, in Balham, London, October 15, 1940. (Photo by AP Photo)

Indian commuters travel in a local train in Kolkata, India, Tuesday, February 26, 2013. Indian Railway Minister Pawan Kumar Bansal is presenting the country's rail budget for next fiscal year in the parliament Tuesday, Feb. 26, 2013. Indian railway network is one of the world's largest, with some 14 million passengers daily and some 64,000 kilometers (40,000 miles) of railway track cut through some of the most densely populated cities. (Photo by Bikas Das/AP Photo)

“Winter shapes, Moscow river”. Moscow river at this part is never covered by ice. When the temperature is very low it's possible to see a strong fog. Morning light and pipes of the oli factory creates a fantastic landscape. Photo location: Moscow, Russia. (Photo and caption by Sergey Rumyantsev/National Geographic Photo Contest)

Cowboy Alexis Azeituno, 25, from Guatemala, gets ready to ride a bull during the International Livestock Fair Show in Havana March 22, 2015. (Photo by Alexandre Meneghini/Reuters)

“Elat’ma, the Ryazan Oblast region of Russia. This small town is only 300 kilometers (186 miles) from modern Moscow but remains 60 years in the past, dominated by the spirit of socialism. The air of the communist ‘50s can be seen in the town’s architecture, celebrations and other occurrences. But neither its beauty nor its ties to a socialist past brought photographer Anastasia Rudenko to this village. Elat’ma is unique in that it functions as a town for mentally disabled people”. – Michelle Cohan via CNN. (Photo by Anastasia Rudenko)

The Leshan Giant Buddha, a 71-metre tall stone statue, is carved out of a cliff face in the southern part of Sichuan province in China. (Photo by Suchet Suwanmongkol/500px)