Cosmic ray and magnetic monopole research. The gallery housing the MACRO (Monopole Astrophysics and Cosmic Ray Observatory) experiment in the Gran Sasso Laboratory, Italy, the largest underground laboratory in the world. MACRO is aimed at detecting magnetic monopoles, exotic particles never seen so far, and highly energetic muons produced by the interaction between cosmic rays and atoms in the upper atmosphere. The Gran Sasso Laboratory lies under 1400m of rock which has a low level of natural radioactivity and shields the detectors from low-energy particles created in the atmosphere by the cosmic rays.