It's housed in a 27-kilometer long tunnel near Lake Geneva, straddling the border of Switzerland and France. Built over the course of 20 years by the European physics consortium CERN, it contains 1,200 superconducting magnets and four detection chambers. Protons will be shot through the tunnel at speeds just short of the speed of light. The magnets, each of which must be cooled to 456 degrees below zero Fahrenheit, keep the speeding protons on track before they collide in the detection chamber, releasing enormous amounts of energy and, hopefully, providing enormous amounts of insight into how the universe is constructed.
The Large Hadron Collider is scheduled to begin operation in early summer.