The light at the end of the tunnel ... View of the north entry to the tunnel "Wannseebahntunnel", located between the stations "Julius-Leber-Brücke" and "Schöneberg" of the Berlin S-Bahn. This tunnel was built in the late 1930ies as part of the North-South-S-Bahn line as underpass for the Wannsee line, which no longer ended in the Wannseebahn part of the station Potsdamer Bahnhof, but was diverted into the tunnel leading via Anhalter Bahnhof. Both the Wannseebahnhof and the line as a whole were located to the west of the Potsdam main line. So the Wannseebahn line had to cross from the southern mouth of the North-South-S-Bahn tunnel to the west of the Potsdam main line...