Gran Sasso mountain in Abruzzo, Italy, site of the Gran Sasso National Laboratory (LNGS). The LNGS is one of four INFN (Italian national institute of nuclear physics) laboratories. It is located inside the mountain, next to the long road tunnel passing through it. The site consists of three large experimental halls, each about 100 metres long, 20 metres wide and 18 metres. The mountain shields the experiments from outside radiation, allowing particle physicists and astrophysicists to study rare interactions involving neutrinos and other particles.