Railway Gazette reported that a groundbreaking ceremony in Berlin on June 6th 2011 marked the start of work on tram and S Bahn connections to the Hauptbahnhof.

A 23 kilometers long tram route will be built along Invalidenstrasse linking Nord bahnhof with Hauptbahnhof by 2015, while a new north-south S Bahn line designated S21 would connect Potsdamer Platz to Westhafen and Wedding via Hauptbahnhof (RG 9.08 p561).

Line S21 is costed at EUR 353 million and will be built in two phases; the Y shaped 3 kilometers long link from Wedding and Westhafen to Hauptbahnhof should open in 2017 while completion of the 19 kilometers extension south to Potsdamer Platz is envisaged in 2022.

(Sourced from www.railwaygazette.com)