The big circle marks the location of the Large Electron-Positron (LEP) collider at CERN, the European Laboratory for Particle Physics. The tunnel in which the particles are accelerated is located 100 m (320 ft) underground and is 27 km (16.7 mi) in circumference. The smaller circle is the site of the smaller proton-antiproton collider. The border of France and Switzerland bisects the CERN site and the two accelerator rings.
