Aerial view of flower fields near the Keukenhof park, also known as the Garden of Europe, in Lisse April 9, 2014. Keukenhof, employing some 30 gardeners, is considered to be the world's largest flower garden displaying millions of flowers every year. (Photo by Yves Herman/Reuters)

A man poses standing on a rock looking at the aurora borealis, or northern lights, illuminating the night sky at Embleton Bay in Northumberland, England, on February 27, 2014. The northern lights is a fantastical natural light display with fast moving light effects caused by particles charged by the sun colliding with particles in Earth's upper atmosphere. (Photo by Tom White/PA Wire)

An African immigrant tries to jump a fence into a ferry terminal in the western Greek town of Patras April 28, 2015. Afghan, Iranian and Sudanese immigrants, living precariously in abandoned factories in Patras, southwest Greece, try to stow away on nearby ferries to Italy as they seek a better life in Europe beyond crisis-hit Greece. (Photo by Yannis Behrakis/Reuters)

A woman is supported by two men while crossing a river, north of Idomeni, Greece, as migrants attempt to reach Macedonia on a route that would bypass the border fence, Monday, March 14, 2016. Hundreds of migrants and refugees walked out of an overcrowded camp on the Greek-Macedonian border Monday, determined to use a dangerous crossing to head north. (Photo by Vadim Ghirda/AP Photo)

Ice covered leafs are pictured on a tree near Amstall in northern Austria, December 2, 2014. Freezing fog and rain covered parts of the region with ice, causing blocked roads due to fallen trees and closed schools for security reasons, local media report. (Photo by Heinz-Peter Bader/Reuters)

In this photo taken on Thursday, July 23, 2015 migrants enter a train to Serbia at the railway station in the southern Macedonian town of Gevgelija. The country has become a major transit route for thousands of Middle Eastern and African refugees and migrants who cross over from Greece and then continue into Serbia. (Photo by Boris Grdanoski/AP Photo)

People walk along the Dune du Pilat (Dune of Pilat), the tallest sand dune in Europe, in La Teste de Buch, near Bordeaux, France, June 15, 2016. The dune has a volume of about 60,000,000 m³, measuring around 500 m wide from east to west and 2.7 km in length from north to south. Its height is currently 110 meters above sea level. (Photo by Sergio Perez/Reuters)

Bebe Rexha performs on stage at the 2016 MTV Europe Music Awards at the Ahoy Arena in Rotterdam, Netherlands, November 6, 2016. (Photo by Yves Herman/Reuters)