Vardzia is a cave monastery site in southern Georgia, excavated from the slopes of the Erusheti Mountain on the left bank of the Mtkvari River, thirty kilometres from Aspindza. The main period of construction was the second half of the twelfth century. The caves stretch along the cliff for some five hundred metres and in up to nineteen tiers. The Church of the Dormition, dating to the 1180s during the golden age of Tamar and Rustaveli, has an important series of wall paintings. The site was largely abandoned after the Ottoman takeover in the sixteenth century. Now part of a state heritage reserve, the extended area of Vardzia-Khertvisi has been submitted for future inscription on the UNESCO World Heritage List

A member of staff stands in front of a CRH high-speed train at Shanghai Hongqiao Railway Station during its test run on May 11, 2011 in Shanghai, China. After 3 years construction, from April in 2008, with total investment estimated at 220.9 billion yuan (around 32.5 billion U.S. dollars), the Beijing-Shanghai high-speed railway begins a one-month trial operation. It is expected to start operation in June this year, with the travel time between the two cities reducing to five hours from the previous 10. (Photo by ChinaFotoPress/Getty Images)

Riders negotiate a dune as they compete in the Adult Solo race at the HydroGarden Weston Beach Race in Weston- super- Mare, south west England, on October 9, 2016. Beach racing is an offshoot of enduro and motocross racing. Riders on solo motorcycles and quad bikes compete on a course marked out on a beach, with man- made jumps and sand dunes being constructed to make the course tougher. (Photo by Adrian Dennis/AFP Photo)

A work by Chinese artist ROBBBB is seen on a wall in the ruins of a building in Beijing September 27, 2015. The 25-year-old artist in Beijing prefers to display his work on the walls of abandoned buildings, rather than a gallery. His artwork is mostly derived from photos of people he sees in the Chinese capital, anyone ranging from elderly people to construction workers. (Photo by Jason Lee/Reuters)

The Mano de Desierto is a large-scale sculpture of a hand located in the Atacama Desert in Chile, 75 km to the south of the city of Antofagasta, on the Panamerican Highway. The nearest point of reference is the “Ciudad Empresarial La Negra” (La Negra Business City). The sculpture was constructed by the Chilean sculptor Mario Irarrázabal at an altitude of 1,100 meters above sea level. Irarrázabal used the human figure to express emotions like injustice, loneliness, sorrow and torture. Its exaggerated size is said to emphasize human vulnerability and helplessness. The work has a base of iron and cement, and stands 11 metres (36 ft) tall. Funded by Corporación Pro Antofagasta, a local booster organization, the sculpture was inaugurated on March 28, 1992.

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)

Wind turbines stand in the Baltic 1 offshore wind farm on April 29, 2011 in the Baltic Sea near Zingst, Germany. Baltic 1, a project of German energy utility EnBW that includes 21 turbines rated at 2.3 megawatts each, will be Germany's first commercial offshore wind farm once it officially begins operation on May 2. Germany has thus far lagged in offshore wind farm construction when compared to neighbors like Great Britain and Denmark, though German Chancellor Angela Merkel has vowed to invest heavily into offshore wind farms as part of an overall policy to encourage renewable energy production. (Photo by Joern Pollex/Getty Images)

A concept illustration of the world's first forest in the sky, the Bosco Verticale green twin towers currently under construction in Milan, Italy. Towering over the city skyline the world's first forest in the sky will be a sight to behold. With tree equal to one hectare of forest spanning 27 floors these 365 and 260 foot emerald twin towers will be home to an astonishing 730 trees, 5,000 shrubs and 11,000 ground cover plants. (Photo by Boeri Studio)