In what city is the 5,500-capacity indoor arena that once hosted a West German disco-era vocal group located? 
Saarlandhalle: Saarlandhalle is a 5,500-capacity multi-purpose indoor arena located in Saarbrücken, Germany. Saarlandhalle:  It has hosted concerts by many famous artists, including A-ha, AC/DC, Chris De Burgh, Depeche Mode, Bob Dylan, Boney M., Metallica, Pink Floyd, Sting and Uriah Heep, among others.
i don't know