A large variety of weapons were for sale at the Washington County Fairgrounds Gun Show that drew thousands of people over the weekend, on March 22, 2013. (Photo by Gary Porter)

Soldiers are reflected in a puddle during a military parade during the celebrations for Romania's National Day in Bucharest December 1, 2014. (Photo by Radu Sigheti/Reuters)

Revellers take part in an annual block party before Carnival in downtown Rio de Janeiro, Brazil, January 16, 2016. The Rio de Janeiro Carnival will be held from February 5 to February 9. (Photo by Pilar Olivares/Reuters)

Battersea Power Station. The chimney rims are thinner on top than you might expect. (Photo by Bradley L. Garrett)

The Berenson robot strolls among visitors during the exhibition “Persona : Oddly Human” at the Quai Branly museum in Paris, France, February 23, 2016. The Berenson robot, developed in France in 2011, is the brainchild of anthropologist Denis Vidal and robotics engineer Philippe Gaussier. Its programming allows it to record reactions of museum visitors to certain pieces of art and then use the data to develop its own unique taste, which allows “Berenson” to judge whether or not it likes a certain work of art within an exhibition. (Photo by Philippe Wojazer/Reuters)

A man looks at a mural painted on the walls of houses in Zaraeeb, created by French-Tunisian artist El Seed, in the shanty area known also as Zabaleen or “Garbage City” on the Mokattam Hills in eastern Cairo, Egypt, April 4, 2016. (Photo by Amr Abdallah Dalsh/Reuters)

Boys pan for gold on a riverside at Iga Barriere, 25 km (15 miles) from Bunia, in the resource-rich Ituri region of eastern Congo February 16, 2009. Ituri is one of many areas of the country to have experienced bitter ethnic conflict between rival tribes in recent years. Massacres have left tens of thousands dead. It is this fighting that led U.S. authorities to take the unprecedented step of naming Congo in section 1502 of the Dodd-Frank financial regulation act, which says U.S.-listed companies that source gold, tungsten, tantalum and tin from Congo or its neighbours must assure the U.S. stock exchange regulator that their business is not helping fund conflict. (Photo by Finbarr O'Reilly/Reuters)

Bosnian worker Sefik Salihovic drives a steam engine in the Bosnian town of Banovici, 140 kms (86.9 miles) north of Sarajevo, on Monday, November 24, 2014. Every day, steam engines over 60 years old, defy their age and still pull wagons of coal from Banovici's coal mine to clients in nearby towns. But in the summer some of them turn into the only tourist attraction this impoverished north Bosnian town has to offer. (Photo by Amel Emric/AP Photo)