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)

People make their way on an algae-covered beach in Qingdao, Shandong province, China, July 19, 2015. (Photo by Reuters/Stringer)

A horse named Quinn, with a skeleton painted on it to help educate officers, is pictured during a visit by Britain's Queen Elizabeth II (unseen) and Britain's Prince Charles, Prince of Wales (unseen) to the Household Cavalry Mounted Regiment at the Hyde Park Barracks in west London on October 24, 2017. (Photo by Chris Jackson/AFP Photo)

Participants wearing fantasy costumes attend the 4th Hero Festival in Marseille, France on November 11, 2017. The 4th Hero Festival edition has attracted all sorts of people to role play their favourite characters from all kinds of movies and comic book legends. (Photo by Jean-Paul Pelissier/Reuters)

The Japanese punk rock garage quartet Otoboke Beaver perform at Maggie Mae's at the South by Southwest (SXSW) Music Film Interactive Festival 2017 in Austin, Texas, U.S., March 17, 2017. (Photo by Brian Snyder/Reuters)

Photo taken on September 19, 2015 shows a baby Brazilian opossum at the “Parque Estoril” zoo in Sao Bernardo do Campo of Sao Paulo, Brazil. According to local press, the “Parque Estoril” zoo houses currently 23 orphan cubs of wild animals rescued in the south region of Sao Paulo, victims of illegal wildlife trade or problems caused by urban growth. According to the zoo, all the animals arrived in the last three months, and many of them, not being able to be reintroduced to their natural habitat, will be used as examples in environmental education classes. (Photo by Rahel Patrasso/Xinhua via ZUMA Wire)

A City of Hollywood SWAT team member helps Alex Treacy from a search and rescue truck as she is evacuated from a flooded area on June 12, 2024, in Hollywood, Florida. As tropical moisture passes through the area, areas have become flooded due to the heavy rain. (Photo by Joe Raedle/Getty Images)

A Filipino activist builds an effigy depicting Philippine President Ferdinand Marcos Jr. ahead of Marcos' first State of the Nation Address, in Quezon City, Metro Manila, Philippines on July 24, 2022. (Photo by Lisa Marie David/Reuters)