A woman from the Tarahumara ethnic group cuts firewood with an ax while preparing for winter in Caborachi village, in Guachochi, Mexico, December 17, 2016. (Photo by Jose Luis Gonzalez/Reuters)

A child stands inside a large soap bubble made by a street artist at the Mayor square in central Madrid, Friday, December 9, 2016. (Photo by Francisco Seco/AP Photo)

A woman dressed for la “La Diablada” festival, walks down a road in Pillaro, Ecuador, Friday, January 6, 2017. Local legend holds that anyone who adopts a costume for the celebration and wears it at the event six years in a row will have good luck. (Photo by Dolores Ochoa/AP Photo)

Kandy Freeman participates in a Black Lives Matter protest in front of Trump Tower in New York City, U.S. January 14, 2017. (Photo by Stephanie Keith/Reuters)

Military items for women are seen in a store in Erbil, Iraq January 24, 2017. (Photo by Marius Bosch/Reuters)

A Palestinian man rides his horse on a beach in Gaza City February 17, 2017. (Photo by Mohammed Salem/Reuters)

The television tower is pictured in Berlin, Germany, May 29, 2016. (Photo by Hannibal Hanschke/Reuters)

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)