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 spooky sight to behold! This is what a psychiatric hospital that has been abandoned for years looks like. Complete with bowling alley and a theater, the hospital shows just how much nature has weathered it over time as paint peels from the walls and the mattress gather dust. Here: This area of the hospital was last used as a day care center in the early 2000s. (Photo by Will Ellis/Caters News)

For centuries the Highlands peoples of Papua New Guinea fought over land, women and pigs. Sorcery and battle skills could elevate a clan to Bigmanship, where the bigger the “presentation”, the bigger the man. Clans therefore would paint their bodies and create fearsome masks as part of their psy. Here: These are the terrifying tribe of “mudmen” from a remote part of Papua New Guinea. (Photo by Jeremy Hunter/Exclusivepix Media)

Volunteers transport an inflated sphere into a canoe to be lowered in MacArthur Park Lake during the installation of Portraits of Hope's exhibition “Spheres at MacArthur Park” in Los Angeles, California August 21, 2015. The installation will feature about 3,000 inflatable hand-painted spheres. (Photo by Mario Anzuoni/Reuters)

Vardzia is a cave monastery site in southern Georgia, excavated from the slopes of the Erusheti Mountain on the left bank of the Mtkvari River, thirty kilometres from Aspindza. The main period of construction was the second half of the twelfth century. The caves stretch along the cliff for some five hundred metres and in up to nineteen tiers. The Church of the Dormition, dating to the 1180s during the golden age of Tamar and Rustaveli, has an important series of wall paintings. The site was largely abandoned after the Ottoman takeover in the sixteenth century. Now part of a state heritage reserve, the extended area of Vardzia-Khertvisi has been submitted for future inscription on the UNESCO World Heritage List

“One artist doesn’t mind if people class her work as rubbish. Thats because all of her pieces are made out of junk found in charity shops, garage sales and in and around her home. Using the likes of buttons, broken jewelry and toy parts, Jane Perkins, from Exeter, UK, has recreated the famous faces of Albert Einstein, Kate Middleton, The Queen, as well as some of the worlds most iconic paintings and photographs”. – Caters News. Photo: Afghan Girl (based on photograph by Steve McCurry/National Geographic). (Photo by Jane Perkins/Caters News)