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Aerial view of CERN and the surrounding region of Switzerland and France. Three rings are visible, the smaller (at lower right) shows the underground position of the Proton Synchrotron, the middle ring is the Super Proton Synchrotron (SPS) with a circumference of 7 km and the largest ring (27 km) is that of the former Large Electron and Positron collider (LEP) accelerator with part of Lake Geneva in the background.