Your home base during your trip! U1 connects you with Kreuzberg and West Berlin, the S-Bahnhof (Sneltrein station) with the entire city, the Tram stops with mostly East Berlin.
S-Bahn and U-Bahn (U1,U3) stations are separate, despite transport maps showing this as one. Linked by an elevated pedestrian bridge. Tram stop can be found outside the U-Bahn station.