This line was transformed into a tram line in 1939 and should be put underground in the sixties when the city decided to follow Munich's example and built a full U-Bahn system. Maps also show a U11, which is used for trains not running the entire route during peak hours only. Apart from Muggenhof and Stadtgrenze all stations have a central platform. Station design is very functional, the only outstanding station being Lorenzkirche showing stone rosettes from the church above. This line is entirely underground although daylight can be seen at Opernhaus station which is open to one side towards the city wall moat.
All stations have central platforms.
This new line might be operated automatically. U21 is used for rush hour trains between Hauptbahnhof and Nordostbahnhof . S3 south to Roth is under construction. The U-Bahn system is easily accessible with elevators and escalators in all stations. Tickets have to be bought from the automatic ticket machines at station entrances and then be cancelled before entering the station.