A concert hall is a cultural building with a stage which serves as a performance venue and an auditorium filled with seats. While early halls built in the 18th and 19th century were designed for classical orchestra, concerto and opera concerts and ballet performances, halls built in the 20th and 21st century were often built to accommodate a wider range of performance types, including musicals. In the 2010s, popular music such as rock music and traditional music such as folk music are also performed in these venues. Many concert halls exist as one of several halls or performance spaces within a larger performing arts center. In many towns, the concert hall is combined with a convention center. Concert halls typically also contain orchestral rehearsal rooms. Many larger cities have both public and private concert halls. Particularly in smaller cities with fewer alternative venues, concert halls may also be used to accommodate other activities, from theatrical performances to academic presentations and university graduation ceremonies.