S7 is a line on the Berlin S-Bahn. It operates from Ahrensfelde to Potsdam over:
the Wriezen Railway, completed on 1 May 1898 and electrified to Marzahn in 1976, to Mehrower Allee in 1980 and to Ahrensfelde in 1982,a section of the Outer ring, completed in the early 1940s as part of the Outer freight ring and electrified in 1976,a section of the Prussian Eastern line, opened on 1 October 1866 and electrified on 6 November 1928,the Stadtbahn, opened on 7 February 1882 and electrified on 11 June 1928,a section of the Berlin-Blankenheim line, opened west of Grunewald in 1879 and further east in 1882 and electrified in 1928 anda section of the Berlin-Potsdam-Magdeburg line, opened in 1838 and electrified in 1928.