The four main LHC experiments 1999 This diagram shows the locations of the four main experiments (ALICE, ATLAS, CMS and LHCb) that will take place at the LHC. Located between 50 m and 150 m underground, huge caverns have been excavated to house the giant detectors. The SPS, the final link in the pre-acceleration chain, and its connection tunnels to the LHC are also shown. PHOTOLAB