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)

A girl washes the body paint off her arm on the shore of Lake Balaton during the coinciding Strand Festival and B.My.Lake Festival in Zamardi, 110 kms southwest of Budapest, Hungary, 24 August 2016. (Photo by Zoltan Balogh/EPA)

A girl poses at an entrance of her house next to a bomb dropped by the U.S. Air Force planes during the Vietnam War, in the village of Ban Napia in Xieng Khouang province, Laos September 3, 2016. From 1964 to 1973, U.S. warplanes dropped more than 270 million cluster munitions on Laos, one-third of which did not explode, according to the Lao National Regulatory Authority. (Photo by Jorge Silva/Reuters)

An Indian girl cries as a medical worker collect her swab sample for COVID-19 test at a rural health center in Bagli, outskirts of Dharmsala, India, Monday, September 7, 2020. India's coronavirus cases are now the second-highest in the world and only behind the United States. (Photo by Ashwini Bhatia/AP Photo)

Two girls dressed up for a night out in Newcastle, United Kingdom on November 01, 2020 – just hours after Boris Johnson's announcement. Johnson says the new measures will begin on Thursday and last until second of December. (Photo by North News and Pictures/The Sun)

In this Thursday, November 1, 2018, photo, a girl uses a hammer to crack open shells for edible seeds to sell as snacks in Yangon, Myanmar. A United Nations report says some 486 million people are malnourished in Asia and the Pacific, and progress in alleviating hunger is stalling. (Photo by Thein Zaw/AP Photo)

A girl calls to her mom as she stands near a dead whale on the shore Monday morning, April 25, 2016, on the cobblestone beach at Lower Trestles on San Onofre State Beach, just south of San Clemente, Calif. (Photo by Jeff Gritchen/The Orange County Register via AP Photo)

A woman and a girl dressed in historical Red Army uniform, wait before watching the Victory Day parade, marking the 71st anniversary of the victory over Nazi Germany in World War Two, at Red Square in Moscow, Russia, May 9, 2016. (Photo by Grigory Dukor/Reuters)