Question: In what city is the 5,500-capacity indoor arena that once hosted a West German disco-era vocal group located? 

Context paragraphs:
Casino Miami: Casino Miami (formerly known as Miami Jai-Alai Fronton) is a 6,500-capacity indoor arena and casino located at 3500 NW 37th Avenue in Miami, Florida.  It is primarily used for gambling, jai alai and concerts.  Notable past performers include The Allman Brothers Band, Black Sabbath, Bruce Springsteen and Frank Sinatra.

Ernst-Merck-Halle: Ernst-Merck-Halle was a 5,600-capacity indoor arena located in Hamburg, Germany, that was opened in 1950 and demolished in 1986.  It was named after German businessman and politician Ernst Merck.  Artists that appeared at the hall include The Beatles, The Rolling Stones, Iron Maiden, Queen, Pink Floyd, The Who and Deep Purple.  The building was demolished in June 1986.

Eissporthalle an der Jafféstraße: Eissporthalle an der Jafféstraße was a 6,000-capacity indoor arena located in Charlottenburg-Wilmersdorf, Berlin, Germany.  It opened in 1973 and was home to Berliner Schlittschuhclub.  The arena also hosted concerts, most notably the last performance by Led Zeppelin on 7 July 1980 before their reunion concert on 10 December 2007.  The building was demolished in 2001.

Veterans Memorial Coliseum (Portland, Oregon): Veterans Memorial Coliseum (formerly and still commonly known as Memorial Coliseum) is a 10,407-capacity indoor arena located in the oldest part of the Rose Quarter area in Portland, Oregon.

Rhein-Neckar-Halle: Rhein-Neckar-Halle is a 8,000-capacity indoor arena located in Eppelheim, Germany.  During the 1970s and 1980s some of the biggest acts in the music industry performed at the venue, including Frank Zappa, Tina Turner, ZZ Top, Genesis, Rush and AC/DC.  It was built in 1970.  Today it is primarily used for sports for the adjacent high school.

Bristol Arena: Bristol Arena is a proposed 12,000-capacity indoor arena, next to Bristol Temple Meads railway station in Bristol, England.  It is due to open in 2020.  The site, which has become known as 'Arena Island', is to the south and across the River Avon from the station, and lies within Bristol Temple Quarter Enterprise Zone.  The funding package for the arena scheme was approved by Bristol City Council in February 2014.  The winning design, by Populous, was revealed in March 2015.

Rijnhal: Rijnhal is a 5,000-capacity indoor arena located in Arnhem, Netherlands.  The arena opened in 1972 and is primarily used for sports and concerts.  Past notable artists that have performed at Rijnhal include Bon Jovi, Alice Cooper, Scorpions and Aerosmith.

Metro Ice Arena: Metro Ice Arena was a 4,600-capacity indoor arena located in Lansing, Michigan.  It hosted the International Hockey League's Lansing Lancers in the 1974-75 season.

Boney M.: Boney M. is a vocal group created by German record producer Frank Farian.  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.  The group was formed in 1976 and achieved popularity during the disco era of the late 1970s.  Since the 1980s, various line-ups of the band have performed with different personnel.

Saarlandhalle: Saarlandhalle is a 5,500-capacity multi-purpose indoor arena located in Saarbrücken, Germany.  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.  Since the introduction of the new stage set in 2001, the hall is too small to host televised concerts.  In 2017 it hosted the 2017 German Darts Open.

Supporting paragraphs: Saarlandhalle Boney M.
Answer: Saarbrücken, Germany