A snowflake rests on black velvet after a snowfall in Knoxville on Tuesday, January 28, 2014. (Photo by Adam Lau/News Sentinel)

A young boy adjusts his friend's Adolf Hitler mask during a game on a street in King's Cross, London. (Photo by William Vanderson/Getty Images). 1938

A general view of the Burj Khalifa on February 23, 2012 in Dubai, United Arab Emirates. At 829.84 m (2723 ft) tall the Burj Khalifa is currently the tallest building in the world. (Photo by Chris Jackson/Getty Images)

Seven month old Christine Joy shares her pram with two 5 week old Gunsure Golden Cherry's cocker spaniel pups from Gunsure Kennels in Ashford, Middlesex. 22nd May 1953. (Photo by Fred Morley/Fox Photos)

A Viet Cong suspect holds his hands up after a Vietnamese Ranger from the 21st Vietnam Infantry Division routed him from his hiding place. (Photo by Keystone/Getty Images). 7th November 1967

A young girls holds a ballot during the Greek referendum in Athens on July 5, 2015. Greek voters headed to the polls today to vote in a historic, tightly fought referendum on whether to accept worsening austerity in exchange for more bailout funds, in a gamble that could see it crash out of the euro. (Photo by Aris Messinis/AFP Photo)

A picture made available on 17 July 2015 shows the bright line of the Milky Way above the old oaks at the Rogalin landscape Park in Rogalin village, near Poznan, on the night of 16 July 2015. (Photo by Lukasz Ogrodowczyk/EPA)