Alexanderplatz in September 1931, seen from the top of Georgenkirche (damaged during the Second World War and demolished later).Friedrich Seidenstücker, the photographer, captured Peter Behrens’s Alexanderhaus (left) and Berolinahaus (right) as well as new U-Bahn tunnels (later only one, current U5, would be used) under construction.Here is the exact location of the scene from Seidenstücker’s photo marked on the map of Alexanderplatz with both new U-Bahn tunnels delineated.

Linie F II (later to be renamed U10), which was meant to connect Berlin-Lankwitz in the south-west with Berlin-Weißensee in the north-east was never built.