The National Theatre of Catalonia opened in the city in 1996. The building resembling a Greek temple was designed by Ricardo Bofill, the famous Catalan architect who projected Barcelona Airport or will build the hotel Vela in the new mouth of the port. With a capacity of 894 seats, the main auditorium has a classical amphitheater shape. If you want to know more about theater in Catalonia you can read this excellent article.
Aerial View of Barcelona's National Theater of Catalonia (Google Earth Image)