The U-Bahn platforms are served by the U5, running from Hauptbahnhof to Hönow via Alexanderplatz. It was opened on 8 August 2009 as line U55, a shuttle to Brandenburger Tor via Bundestag, the only intermediate station. This line was operated as a single-track shuttle, and only one of the two platform tracks was used, the other being behind a metal fence, mounted in the ground. Construction of a connection to line U5 commenced in April 2010 and opened to the public on 4 December 2020. In the long term it is planned to extend the U5 from the main station towards the west to Turmstraße and Jungfernheide. Due to lack of funds from the state of Berlin, the northwestern continuation is not expected in the near future.