The original layout of the streets on the acropolis and the defensive walls, both there and on the northern hill, went back to the late VI or early V centuries B.C.; but much that is visible today is the result of subsequent rebuilding, either to strengthen the defences according to the developing requirements of warfare, or to patch up, sometimes very hastily, what had been destroyed.

Perhaps the finest stretch which mat belong to the original walls is the high, stepped wall on the east side of the acropolis.
Rising to a height of about 12 m, it is stepped back from the outer facade, and must once have been topped by a vertical wall.

Further north on the same side the acropolis has been strengthened with a counterwall and towers, thought to date from the early IV century.