U1 is a line on the Berlin U-Bahn, which is 8.8 kilometres (5.5 mi) long and has 13 stations. Its traditional line designation was BII. It runs east–west and its eastern terminus is Warschauer Straße S-Bahn station where it connects to the Schlesische Bahn. From there it runs through Kreuzberg via Gleisdreieck and Wittenbergplatz on to the Kurfürstendamm. The eastern section of the line is the oldest part of the Berlin U-Bahn, although it is largely above ground.