German capital city Berlin’s transport operator Berliner Verkehrsbetriebe has approved a €433m project to build an underground extension of metro line U5.

The 2.2km underground section will run between Alexanderplatz and Brandenburger Tor and will link the recently opened 1.5km U55 shuttle between Brandenburger Tor and Hauptbahnhof into line U5.

The project includes building stations at Berliner Rathaus, Museuminsel and Unter den Linden.

Preparatory work is scheduled to begin in early 2010 with the extension expected to open in 2017.