The theatre was first built in the 4th century B.C. It was renovated and enlarged during the Hellenistic age and seating capacity reached to 5,300. Later on, during the Roman period (2nd century A.D.) it was reconstructed and mainly enlarged to 20,000 spectator capacity. The construction differences between Hellenistic and Roman architectural styles are still visible in the ruins of the theatre.
The theatre is supported by the hill behind. The front seats are still well preserved. The royal seats were marked with two pillars which were supported by a baldachino.
The archaic period city ramparts were buried under the front stage section of the theatre. The front rows of seats were usually allocated for influencial citizens of the city. There are still numerous inscriptions on some seats in the front rows indicating owners of the seats.
The stage of the theatre was 140 m wide. The auditorium was 40m high.