27 kilometers of magnets
The two beams of protons will speed through their underground tunnels at a site straddling the border between France and Switzerland (below).
The tubes below house the high-power magnets that guide the beams.
Below, a side view shows the channels through which the beams will accelerate (openings at center of image, one with a cable dangling from it). These two pipes are surrounded by superconducting metal cables (not visible in this image) through which a tremendous electric current flows, creating strong magnetic fields that guide the protons around the LHC and then toward each other for the high-energy collisions. Two tubes for the liquid helium that cools the magnets are visible at the bottom of the cross section.
Credit: AC Team (map); AP/Keyston/Martial Trezzini (tunnel); David Avid Parker/Science Photo Library (magnet)