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 vegetarian festival devotee gets medical attention after a parade at Jui Tui shrine on September 30, 2014 in Phuket, Thailand. (Photo by Borja Sanchez-Trillo/Getty Images)

At the Krasnopresnenskaya station, the benches come from the Cathedral of Christ-Sauveur, which was built from 1839 to 1883 in memory of the victory of Russia against the army of Napoleon I. The cathedral was destroyed under Stalin in 1931, but the benches remained intact. Metro architects decided to install them in some stations. (Photo by Didier Bizet/The Washington Post)

A reveller tries to hold on to a wild horse during the “Rapa Das Bestas” traditional event in the Spanish northwestern village of Sabucedo July 5, 2014. On the first weekend of the month of July, hundreds of wild horses are rounded up, trimmed and groomed in different villages in the Spanish northwestern region of Galicia. (Photo by Miguel Vidal/Reuters)

A South Korean model poses with Peugeot 5008GT during a press preview of the Seoul Motor Show in Goyang, northwest of Seoul, on March 30, 2017. South Korea's largest international auto show will open on March 31, with a total of 27 brands showing their latest cars and concepts. (Photo by Jung Yeon-Je/AFP Photo)

A Citroen Ami One concept car sits on display during the media day of the Auto Shanghai 2019 motor show in Shanghai, China, 16 April 2019. The 18th Shanghai international automobile industry exhibition runs from 16 to 25 April. (Photo by Wu Hong/EPA/EFE)

A transparent van is displayed by a vendor for safety devices at the IAA Auto Show in Frankfurt, Germany, Tuesday, September 10, 2019. (Photo by Michael Probst/AP Photo)

People observe a protest against a new citizenship law from a bus, in New Delhi, India, January 3, 2020. (Photo by Anushree Fadnavis/Reuters)