The Veto system of the OPERA experiment

OPERA is a neutrino oscillation experiment to search the ντ appearance in the future CNGS beam from CERN to Gran Sasso. A large VETO system, consisting of two 9.6 × 9.2 m2 planes made of glass RPCs, is foreseen to flag the events due to the neutrino interactions with the rock surrounding the OPERA detector. We describe the VETO system, its monitoring system, the glass RPC developed.