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)

Camila Iachini, 8, performs with her bike during celebrations for the 400th anniversary of the founding of the neighbourhood Petare, in Caracas, Venezuela on February 17, 2021. (Photo by Leonardo Fernandez Viloria/Reuters)

This undated image provided by World View shows World View capsule and balloon spacecraft that will rise to 100,000 feet above Earth for passengers to see the curvature of the planet and the blackness of space. Space tourism companies are employing designs including winged vehicles, vertical rockets with capsules and high-altitude balloons. While developers envision ultimately taking people to orbiting habitats, the moon or beyond, the immediate future involves short flights into or near the lowest reaches of space without going into orbit. (Photo by World View via AP Photo)

Hidden Britain category winner. Garden Spider by Alan Smith from Reading, Berkshire. (Photo by Alan Smith/British Wildlife Photography Awards/PA Wire Press Association)

A leaflet denouncing South Korean President Park Geun-hye lies on the ground after it was torn at a protest calling Park to step down, in Seoul, South Korea, November 19, 2016. (Photo by Kim Hong-Ji/Reuters)

Music fans attend Day 1 of the Coachella Valley Music & Arts Festival 2011 held at the Empire Polo Club on April 15, 2011 in Indio, California. (Photo by Frazer Harrison/Getty Images)

A military cadet refreshes her lipstick before the National Day parade in Bucharest, Romania, Friday, December 1, 2023. Tens of thousands of people turned out in Romania's capital on Friday to watch a military parade that included troops from NATO allies to mark the country's National Day. (Photo by Vadim Ghirda/AP Photo)

Renowned amphibian and reptile photographer Matthijs Kuijpers has released his first book, “Cold Instinct”. Kuijpers says the aim of the work is “for the viewer to abandon the fear and negative thoughts that often surround these animals”. What’s left is the bizarre beauty of these creatures in their simplest form – no backgrounds and no distractions. Here: Mossy frog (Theloderma corticale). (Photo by Matthijs Kuijpers/The Guardian)