A man holds his umbrella during snowfall on the Areopagitou pedestrian street beneath the Acropolis hill during snowfall in Athens, Greece, January 10, 2017. (Photo by Alkis Konstantinidis/Reuters)

Participants climb over a wall at the “Tough Mudder” endurance event series in Arnsberg September 6, 2014. Competitors who took part in the endurance event saw themselves having to overcome various military style obstacles. (Photo by Ina Fassbender/Reuters)

Decorated veterans take part in the Veterans Day parade in honor of the victory over the Nazi Germany, on May 11, 2011 in Jerusalem, Israel. Hundreds of Jewish World War II veterans from the Allied armies, mostly the former Soviet Union, and Israelis took part in the parade. (Photo by Avi Ohayon/GPO via Getty Images)

Egyptian bootblacks cleaning a European's shoes in Cairo. (Photo by Hulton Archive/Getty Images). Circa 1870

A member of the German wireless police picks up signals on the radio equipment he carries on his back, while his colleague takes notes. (Photo by General Photographic Agency/Getty Images). Circa 1925

A Mark IV tank, part of the parade at the Lord Mayor's Show in London. (Photo by Topical Press Agency/Getty Images). November 1917

A workman takes a siesta on a girder during the building of Radio City, the city of New York spread out below. (Photo by General Photographic Agency/Getty Images). Circa 1933

Ernie Lotinga, looking terrified as a gun is pointed in his face, in a scene from the play “My Wife's Family”, at the Garrick Theatre, London. (Photo by Sasha/Getty Images). 24th February 1941