The CERN Neutrinos to Gran Sasso (CNGS) project was a physics project of the European Organization for Nuclear Research (CERN). The aim of the project was to analyse the hypothesis of neutrino oscillation by directing a beam of neutrinos from CERN's facilities to the detector of the OPERA experiment at the Gran Sasso National Laboratory (LNGS), located in the Gran Sasso mountain in Italy. The CNGS facility was housed in a tunnel which diverged from one of the SPS-LHC transfer tunnels, at the Franco-Swiss border near Geneva. It used the Super Proton Synchrotron (SPS) accelerator as a source of high-energy protons.