The U4 is Berlin's second-shortest U-Bahn line after the U55, linking Nollendorfplatz and Innsbrucker Platz. It has just five stations, and trains usually run as short (2-car) units every ten minutes (increasing to five minutes during the rushhour).

The U4 was built before the First World War, at which time the surrounding district of Schöneberg was still an independent town outside of Berlin. It is a narrow-profile (Kleinprofil) line


U1 Station Nollendorfplatz ( U1, U2, U3)
U1 Station Viktoria-Luise-Platz
U1 Station Bayerischer Platz ( U7 )
U1 Station Rathaus Schöneberg
U1 Station Innsbrucker Platz ( S41/42, S45)