The town is surrounded by a wall - with about 100 towers - of almost 5 kilometers, itself surrounded by a ditch. I here try ands suggest a walk along the walls, with sub-galleries with pictures of gates.
Roughly I start near the lake and at the west side of town, then walk (counterclockwise) sometimes within the walls, sometimes outside.

The wall in Hellenistic times originally enclosed a square and had a total length of 2839 meters. Later it was extended into a polygon, with a total length of 4420 meters. The oldest part is from the times of Hadrian, most of the main wall dates from the third century. It has been constantly extended and repaired.

There is an informative site about the gates.