agreed.
1. city walls - early AM (its HOT!!!)
2. walking tours - meet at fountain. pretty cheap in Kuna.
3. restaurants/walking yourself - check out all those side streets and alleys for the good ones.
i would essentially try to walk in/through/around all the parts of old town. you could wander for a good 2 days or more without even going inside! there' a wicked bar/cafe on the rocks through a tunnel at the back of the old town. i can remember how to get there in my head, but couldn't direct you for beans.