We spent an afternoon in the walled town of Cuenca and found it to be a very lovely and friendly place. However, walking in most historic Spanish towns can be quite strenuous as the roads tend to be steep and one is either walking uphill or downhill. As a result, we walked to the Plaza Major and then took the small sightseeing train. It was reasonably priced and both started and ended in the Plaza Major, concentrating on sights in the historic town. I would recommend this as a good way to get an overview of the walled town of Cuenca before deciding on any specific sights you may want to see.