The attendants of the Sumptha Raja, Agra Durbar. (Photo by Hulton Archive/Getty Images). 1873

Prostitutes working on 10th Ave in New York, USA on June 29, 1997. (Photo by Jon Naso/NY Daily News Archive via Getty Images)

Austrian Bodybuilder and actor Arnold Schwarzenegger has some fun at a party on a yacht in Marina Del Rey in September 1979 in Los Angeles, California. (Photo by Michael Ochs Archives/Getty Images)

An Indian Brahmin and his family. (Photo by Hulton Archive/Getty Images). Circa 1890

Beneath the Swedish capital lies an intricate web of underground train lines. More than 90 of the 100 stations in the 110km tunnel system, sometimes referred to as “the world’s longest art gallery”, have been decorated with paintings, installations, mosaics and sculptures by 150 artists since the 1950s. After spending a couple of weeks exploring arctic Norway and Sweden, London-based travel photographer Conor MacNeill headed underground to capture images of the metro stations. Here: A rainbow arcs over a girl on the platform of Stadion station. (Photo by Conor MacNeill/The Observer)

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

Guests on the terrace of Shepheard's Hotel, Cairo, circa 1940. (Photo by Hulton Archive/Getty Images)

In this photo taken in October 1917, provided by Russian State Documentary Film and Photo Archive, a machine gunner looks through a window at his position near the Kremlin in Moscow, Russia. The 1917 Bolshevik Revolution was long before the digital revolution allowed anyone to instantly document events. But the clumsy cameras of the time still caught some images that capture the period's drama. (Photo by Russian State Documentary Film and Photo Archive via AP Photo)