Construction cranes stand on the Unstrut Valley high-speed railway bridge on March 19, 2012 near Karsdorf, Germany. The Unstrut bridge, which is 2,668m long (about 1.6 miles), is among 38 bridges and 26 tunnels German state rail carrier Deutsche Bahn is building along a new ICE high-speed railroad connection between Nuremberg, Erfurt, Halle, Leipzig and Berlin in a multi-billion Euro project across eastern Germany called the German Unity Transportation Project (Verkehrsprojekt der Deutschen Einheit). (Photo by Sean Gallup/Getty Images)

Lisa Yu crawls through a mud pit under low slung barbed wire as she competes in The Tough Bloke Challenge on March 4, 2012 in Melbourne, Australia. The Tough Bloke Challenge is one of the most gruelling adventure runs in Australia consisting of 18 obstacles over a 6 km cross-country course laden with thick mud-pits and ice-cold water crossings. (Photo by Scott Barbour/Getty Images)

Zahra Lari runs in a scene shot for the Nike Middle East ad campaign filmed in Dubai, UAE, February 10, 2017. An online commercial released by Nike (NKE.N) this week that showed Arab women fencing, boxing and spinning on ice-skates has stirred controversy over its attempt to smash stereotypes about women leading home-bound lives in the conservative region. (Photo by Reuters/Nike)

Two women jump into a frozen pond as they compete in the Polar Plunge at Frozen Dead Guy Days in Nederland, Colorado March 14, 2015. The winter festival in the small mountain town commemorates the 1994 discovery of the corpse of Bredo Morstol, which is now housed in a shed on dry ice above the town. (Photo by Rick Wilking/Reuters)

Earlier this year, Belgian film-maker and artist Vincent Bal stumbled upon an uncanny resemblance to an elephant in the shadow of his tea cup. This gave him the idea for Shadowology, a series of doodles that interact with the shadows of simple, everyday objects: a banknote, some ice cubes and a flower, for example, can turn into a church, a woman and a hippy. “I draw a few lines and I get my image. It’s really the shadows that inspire me”, Bal says. Here: “Stonedog”. (Photo by Vincent Bal/The Guardian)

This undated handout photo received from the Antarctic Ocean Alliance on October 28, 2016 shows a adelie penguin jumping onto the ice in the Ross Sea in Antarctica. The world's largest marine reserve aimed at protecting the pristine wilderness of Antarctica will be created after a “momentous” agreement was finally reached on October 28, 2016 with Russia dropping its long-held opposition. (Photo by John Weller/AFP Photo/Antarctic Ocean Alliance)