A beautiful theatre with a capacity of 6300 audience members at its peak, crowns the western sector of the ancient city. Constructed in the 5th century B.C. following the Persian invasion, it was carved into an artificial hill. Eleven kerkides divided by 10 klimakes (staircases) set out the koilon in the 4th century B.C., while a vaulted underground arcade leading from the stage to the centre of the orchestra, connected the world of the dead with the world of the living.