From another site I got the information: " The stage building of this [Sagalassos] theatre, which could seat some 9000 spectators, was completed during the period 180- 210 AD. Yet, the auditorium is probably older.

It is very unusual that the stage building was only one story high. This was clearly the result from the fact that the whole building is turned towards the flat conical hill in the background, which is the hill upon which in 333 BC Alexander the Great defeated the Sagalassians, a fact they were proud of later. South of the theatre, there was a ca 12 m tall honorific column, possibly carrying the statue of the person, who helped to finance the theatre. Despite its construction date, the theatre clearly continues the Hellenstic building tradition (mostly built on a natural slope, horseshoe-shaped auditorium, stage building and auditorium not connected to each other)." There was a link to the source of this information, but that turned out to be broken.