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. Boney M.:  Originally based in West Germany, the four original members of the group's official line-up were Liz Mitchell and Marcia Barrett from Jamaica, Maizie Williams from Montserrat and Bobby Farrell from Aruba.
i don't know