Asklipio is a great place to visit in Rhodes, not just for the castle. There is also a very impressive church and museum. After parking in the massive lot in the middle of town you walk into the complex and pay your fee. Then you go through a fairly interesting ecclesiastical museum before entering into the the inner courtyard of the complex. There is a folklore museum on the other side of the courtyard but this wasn't open. The highlight is definitely the main church - Kimisis Theotokou - which has very impressive frescoes, though unfortunately no picture are allowed. It reminded me of the church in Lindos.