A tunnel with electric switches are seen in Josip Broz Tito's underground secret bunker (ARK) in Konjic, October 16, 2014. In the early 1950s, Josip Broz Tito, the late leader of the former Yugoslavia, ordered the building of the secret bunker, located 900 feet (270 m) underground and near the Bosnian town of Konjic, to safeguard the country's ruling class in case of a nuclear attack. Construction at the complex, which had a cost equivalent price tag of $4.6 billion, continued until 1979, the year before Tito died. (Photo by Dado Ruvic/Reuters)

Jeremy Davis (L) demonstrates the operation of the safe room shelter door lock to homeowner Rob Hamlin on June 18, 2011 in Neosho, Missouri. Once thought of as a luxury item there has been a surge of interest from homeowners in purchasing shelters to ride out damaging storms ever since a F5 tornado tore through the town of Joplin, Missouri. Ranging in price from $3,000 to $5,000 homeowners can supplement the cost with a mortgage insurance program offered by the U.S. Department of Housing and Urban Development for installing a safe room built to FEMA specifications. Lawmakers in Alabama have even considered requiring construction of storm shelters in mobile home parks after forty people died in April. (Photo by Julie Denesha/Getty Images)

Growing cities, overuse of fertilizers and factory wastewater have degraded China's water supplies to the extent that half the nation's rivers and lakes are severely polluted. China aims to spend $850 billion to improve filthy water supplies over the next decade, but even such huge outlays may do little to reverse damage caused by decades of pollution and overuse in Beijing's push for rapid economic growth. Photo: Fishermen row a boat in the algae-filled Chaohu Lake in Hefei, Anhui province, June 19, 2009. (Photo by Jianan Yu/Reuters)

One of two 9-month old Cheetahs is seen after it was released into a quarantine facility at Zoo Miami on November 29, 2012 in Miami, Florida. The two sub-adult brothers who arrived today were captive-born on March 6th of this year at the Ann van Dyk Cheetah Centre just outside of Pretoria, South Africa. The Cheetahs, after being monitored and examined for a minimum of 30 days to insure that they are healthy and stable, will be featured in Zoo Miami's Wildlife Show at the newly constructed amphitheater and will continue the work of Zoo Miami's Cheetah Ambassador Program by making appearances off Zoo grounds at a variety of venues including schools and civic organizations. (Photo by Joe Raedle)

Li Guoqiang talks on his phone outside his house at Guangfuli neighbourhood, in Shanghai, China, April 1, 2016. Li, 38, is a deliveryman who rents a place at Guangfuli. In a corner of Shanghai, surrounded by a cement wall, lies one of the world's most valuable fields of debris and garbage. On paper, the Guangfuli neighbourhood is a real estate investor's dream: a plot in the middle of one of the world's most expensive and fast-rising property markets. But the reality is more like a developer's nightmare, thanks to hundreds of people living there who have refused to budge from their ramshackle homes for nearly 16 years as the local authority sought to clear the land for new construction. (Photo by Aly Song/Reuters)

French artist Thomas Lamadieu, also know as Roots Art, must really love looking at the sky. Every time he looks up, Thomas sees a potential canvas where the building rooftops frame the sky. He photographs it and uses the odd sky shapes to create whimsical line drawings. “My artistic aim is to show a different perception of urban architecture and the everyday environment around us, what we can construct with a boundless imagination,” says Thomas. (Photo by Thomas Lamadieu)

“The Berlin Wall (German: Berliner Mauer) was a barrier constructed by the German Democratic Republic (GDR, East Germany) starting on 13 August 1961, that completely cut off West Berlin from surrounding East Germany and from East Berlin. The barrier included guard towers placed along large concrete walls, which circumscribed a wide area (later known as the “death strip”) that contained anti-vehicle trenches, “fakir beds” and other defenses. The Soviet-dominated Eastern Bloc officially claimed that the wall was erected to protect its population from fascist elements conspiring to prevent the “will of the people” in building a socialist state in East Germany. However, in practice, the Wall served to prevent the massive emigration and defection that marked Germany and the communist Eastern Bloc during the post-World War II period”. – Wikipedia

Photo: West Berlin policemen and East German Volkspolizei face each other across the border in Berlin, circa 1955. (Photo by Three Lions/Hulton Archive/Getty Images)

A couple hugs while standing near a Christmas tree made out of plastic bins and plastic hampers outside the Museum of History in Monterrey, Mexico, December 4, 2015. The humble Christmas tree has a rich history, from evergreen trees used to symbolise eternal life in Ancient Egypt to tree worship among pagan Europeans. The modern version has its origins in Germany, where the song “O Tannenbaum” is still a festive favourite. Today the traditional tree with lights and decorations appears in cities including Washington, Moscow and Beirut. Alternative constructions range from recycled rubbish in Mexico City to old window frames in Rakvere, Estonia. Whatever the shape or size, the message is the same: Merry Christmas. (Photo by Neil Hall/Reuters)