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)

Bystanders look on as workers arrange silver blue fabric, part of the process of wrapping L'Arc de Triomphe in Paris on September 13, 2021, designed by the late artist Christo. Work has begun on wrapping the Arc de Triomphe in Paris in silvery-blue fabric as a posthumous tribute to the artist Christo, who had dreamt of the project for decades. Bulgarian-born Christo, a longtime Paris resident, had plans for sheathing the imposing war memorial at the top of the Champs-Elysees while renting an apartment near it in the 1960s (Photo by Geoffroy Van der Hasselt/AFP Photo)

View of a light show on the city's iconic Arc de Triomphe monument during the New Year celebration in Paris, France, December 31, 2016. (Photo by Jacky Naegelen/Reuters)

Protesters a demonstration of the LGTBI collective in Madrid on November 20, 2021 against the rise of the fascism in the society and in support of the new transgender law in Spain. (Photo by Celestino Arce Lavin/ZUMA Press Wire/Rex Features/Shutterstock)

A camel rider push his camel in the annual Wadi Zalaga competition between two rival Bedouin tribes in the South Sinai region, Egypt on January 10, 2023. (Photo by Celestino Arce/NurPhoto/Rex Features/Shutterstock)

A demonstrator is detained by police officers during clashes in downtown Barcelona, Spain, Friday, October 30, 2020. Clashes have erupted in a central Barcelona square between anti-riot police and hundreds who had gathered to protest the mandatory closure of bars, restaurants and other businesses in the latest effort to rein in on coronavirus outbreaks. (Photo by Joan Mateu/AP Photo)

Pilgrims ride their horses on their way to the shrine of El Rocio in Villamanrique, Spain, on Saturday, June 4, 2022, during the annual pilgrimage in which hundreds of thousands of devotees of the Virgin del Rocio converge in and around the shrine. (Photo by Joan Mateu Parra/AP Photo)

Barcelona's Caroline Graham Hansen, center, in action during the women's Champions League quarterfinals, second leg, soccer match between FC Barcelona and SK Brann Kvinner at the Estadi Johan Cruyff in Barcelona, Spain, Thursday, March 28, 2024. (Photo by Joan Monfort/AP Photo)