a striking fact is the construction of the "cavea" (gr.: koilo, auditorium) on an artificial hill surrounded by numerous retaining walls, instead of taking advantage of the citadel's slopes. during the first building phase, the scene looked like a palace, disposed of five adjacent rectangle rooms and found itself at the same level as the circular orchestra, leading to it via three entrances. at its peak (fourth century bc), the theatre suffered transformations and was shaped to a large extent in its present form. the cavea comprised eleven tiers divided by ten staircases. the circular orchestra was transferred for 8m to the north, and was lowered by 3m. the scene was amplified by two backstages connected through a portico with an ionic façade, thus raising above the orchestra. this difference in heights was evened up by a vaulted underground gallery, leading through the scene to the centre of the orchestra; this was in all probability the "charonian stairway" (stairs of hades) allowing actors impersonating chthonic deities and the dead to appear and perform at the orchestra.