Complex sentence: Berat Castle, with its 24 towers, is located around the main town in some/built on a rocky hill on the left bank of the Osum and is accessible only from the south.
Split into simpler sentences: Berat Castle, with its 24 towers, is located around the main town. It is built on a rocky hill on the left bank of the Osum, on the area of some, and is accessible only from the south.