Aerial view of the CERN-Meyrin site during building work for the SPS

Visible on the right hand site are three building areas: in front the area around pit 6 of the SPS (where the ejection to the West Area branches off), in the middle the area around the 'civil engineering pit 7', and in the back the area around the SPS pit 1 where injection takes place. The SPS tunnel, 6910 m in length with an inner diameter of 4m in its cross section, is at an elevation of 400 m above sea level corresponding to a depth below the surface which varies between 23 and 65 m. It has 6 regularly spaced access pits. The further pit 7 is situated on the injection line about 200m from the injection point. It was used to extract material excavated from the ring and to bring in the precast elements and the concrete for lining the tunnel with a shell of about 30 cm thickness.