All rail systems serving Stuttgart, the Baden-Württemberg state capital, stop at the main station (Hauptbahnhof) in front of the Arnulf-Klett-Platz (Plaza). This central point is served by all national trains, S-Bahn (Subway) commuter trains, the U-Bahn (Tram system) and busses.  

Stuttgart Hauptbahnhof (main station)
Arnulf-Klett-Platz 70173 Stuttgart[i]
The Hanns-Martin-Schleyer-Halle is about 3 km from the main station.

Bad Cannstatt station
Bahnhofstraße 30 70372 Stuttgart 
The Hallenduo is about 1 km from the Bad Cannstatt station.      

Note: Free use of public transport*.

Suburban trains:
S1 (NeckarPark/Mercedes-Benz stop)
S1, S2, S3 (Bad Cannstatt station stop)

City trains:
U1, U2 (Bad Cannstatt Wilhelmsplatz stop)
U13 (Bad Cannstatt Wilhelmsplatz stop)
U11 (NeckarPark (stadium) stop)
(special line during major events in NeckarPark)
U19 weekdays 7 a.m. to 8 p.m. (NeckarPark (stadium) stop)
(Runs outside these hours as a special line during smaller events at NeckarPark).

Line 45, 56 (NeckarPark (stadium) stop)
Line 52 and X1 (stop Bad Cannstatt Wilhelmsplatz)

*applies to almost every event. Please note the information on your ticket.