Musiktheater im Revier (MiR) (Music Theatre in the Ruhr) is the venue for performing opera, operetta, musical theatre and ballet in Gelsenkirchen, Germany. It opened on 15 December 1959; it is listed since 1997 as a protected cultural monument. The building offers two performance spaces: the Large House (Großes Haus) with 1,008 seats and about 200 performances per year, and the Small House (Kleines Haus) with 336 seats and about 120 annual performances. In contrast to the building's outside cubic appearance, the auditoria use a more curved design.