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)

Axel, a research prototype rover for exploring the Moon, Mars and other planets, is remotely driven over rocks as engineers from Jet Propulsion (JPL) and grad students from Caltech (California Institute of Technology) demonstrate its mobile over the steep and rocky grounds of the JPL Mars Yard on January 14, 2009 in Pasadena, California. The rover is capable of descending cliffs or into craters and returning by a cable tethered to its starting point. Development of the Axel rover is a point effort funded by NASA Exploration Systems Mission Directorate (ESMD) and lead by Principal Investigator Issa Newnas and Co-Investigator and Caltech professor of mechanical engineering bio engineering Joel Burdick. (Photo by David McNew/Getty Images)

Bex Hetherington exhibits a T-shirt at the Edinburgh College of Art degree show on June 8, 2011 in Edinburgh, Scotland. Students work will be exhibited across the campus buildings turning Edinburgh College of Art into the city's biggest gallery space. The work ranges from conceptual to commercial with inspirational influences as diverse and wide ranging as fashion photography, volcanoes, the crazy lady who put a cat in a bin, fairytales, the star system and serial killers. (Photo by Jeff J Mitchell/Getty Images)

A protester holds a sign in front of riot policemen during an anti-G20 demonstration through the streets of Nice on November 1, 2011 in Nice, France. Anti-G20 demonstrators are gathered in Nice ahead of the arrival of the world's top economic leaders for the G20 summit in Cannes on November 3rd and 4th. The leaders are expected to debate current issues surrounding the global financial system in the hope of fending off a global recession and finding an answer to the Eurozone crisis. (Photo by Christopher Furlong/Getty Images)

Wim Delvoye is a notorious tattoo artist, who became famous when he started tattooing live pigs. He first began in 1997 and after animal rights activists found out about what he was doing, he had to move to China to continue his business. There is nothing special about the tattoos that Wim Delvoye creates, they look mediocre at best, and the only reason why he’s famous is his acts of animal cruelty. Nevertheless, Wim states that the pigs feel just fine and are well fed and taken care off. Full anesthesia is used to ensure that the pig doesn’t feel pain during the course of the whole procedure. During this time three tattoo artists work on the tattoo simultaneously to complete it as quickly as possible. Skins of those pigs are then sold for as much as £50k a piece.

Most Russians intending to vote for Vladimir Putin in Sunday's election say stability is at the root of their faith in their candidate – though many young voters believe it's time for a change of leader. Putin, 65, is expected to win a fourth term in office with 69 percent of the vote, according to the latest survey by a state-run pollster. Reuters correspondents and photographers who travelled around the country talking to voters ahead of the March 18 election found nothing to contradict expectation of an emphatic Putin victory. (Photo by Anton Vaganov/Reuters)

Photographs show an adventurer swimming with giant Manta Rays at night. In her latest daring adventure, Alison Teal set out in the middle of the night to free dive with Manta Rays off the coast of Hawaii. Using only hand held dive lights, Alison dove over 50 feet down being careful never to touch the mantas as they fed off the plankton in the light streams. Here: Photos taken by photographer Sarah Lee show the beautiful sight of Manta Rays at night, as they swim with America explorer, Alison Teal. (Photo by Sarah Lee/Caters News Agency)

“The Six-Day War or June War, also known as the 1967 Arab-Israeli War or the Third Arab-Israeli War, was fought between June 5 and June 10, 1967, by Israel and the neighboring states of Egypt (known then as the United Arab Republic [UAR]), Jordan, and Syria. The war began with a large-scale surprise air strike by Israel on Egypt. The outcome was a swift and decisive Israeli victory. Israel took effective control of the Gaza Strip and the Sinai Peninsula from Egypt, the West Bank and East Jerusalem from Jordan, and the Golan Heights from Syria. Opinions are divided on whether Israel's attack was an act of aggression or a preemptive strike of a defensive nature”. – Wikipedia

Photo: The corpse of a soldier lying on the line of the Israeli advance into Syria during the Six-Day War. (Photo by Terry Fincher/Getty Images). 1967