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)

The Jumbo Stay blends into the background at Stockholm Arlanda Airport. If you spot it as your plane rolls along a taxiway, you might notice an aging widebody jet parked by its lonesome self in a secluded part of the airport.

A model walks down the runway during the Odd Molly Autumn/Winter 2012 Fashion Show at Berns on February 1, 2012 in Stockholm, Sweden. (Photo by Ian Gavan/Getty Images)

A model walks down the runway during the Safilo fashion show at the Mercedes-Benz Fashion Pavilion on January 30, 2012 in Stockholm, Sweden. (Photo by Ian Gavan/Getty Images)

A charity runner dressed as Father Christmas steps out of a portable toilet ahead of the “Santa Run” charity fun run in Stockholm on December 10, 2017. Hundreds of participants dressed in Santa suits and wearing white beards ran through the streets of the old town in Stockholm in an all charity run. (Photo by Jonathan Nackstrand/AFP Photo)

A woman dressed up as a zombie participates in a zombie walk in Stockholm, Sweden on August 19, 2017. (Photo by Jonathan Nackstrand/AFP Photo)

Eurovision fans from Sweden kiss in front of the Globen Arena prior the first the Eurovision Song Contest final in Stockholm, Sweden, Saturday, May 14, 2016. (Photo by Martin Meissner/AP Photo)