ÖSTU-STETTIN is building the Filder Tunnel and the Ober-Untertürkheim Tunnel, with a respective length of 9.5 and six kilometres, as part of the centennial ‘Stuttgart 21’ project. They are important feeders for the terminus station, which will be transformed into an underground through-station when fully operational. Tunnelling under the Neckar River is a particular challenge in this respect.
