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A section of the 27Km circular tunnel beneath the French-Swiss border near Geneva. The tunnel carries the Large Hadron Collider particle accelerator which houses two beams of protons, within separate high-vacuum pipes, travelling in opposite directions, kept on an accurate path by dipole super-conducting electromagnets, cryogenically chilled to -271.3ºC by liquid helium. Photographed during the 2013 shutddown, with the main vacuum pipe open for maintenance work.