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. 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. Boney M.:  The group was formed in 1976 and achieved popularity during the disco era of the late 1970s.
Saarbrücken, Germany