FRANKFURT – Between Lake Geneva and the Swiss Jura, more than 100 meters (328 feet) below the surface, lies a circular tunnel, 27 kilometers (17 miles) in circumference, containing superconducting magnets that accelerate protons almost to the speed of light. At four locations in the tunnel, the protons are made to collide. Particle physicists observe these collisions, in an effort to learn what matter is made of and what holds it together.