We just finished spending two nights here (one full day). I was worried that we wouldn't find anything to do all day...boy, was I wrong! We went up to the castle/fortress (what is the correct term?) around 10am and were there until about 2-3pm. Wandering around the walls, did the audio tour, had some lunch and did some shopping. The little shops are lovely. Back to our room for a little rest. Then we went to the 'big' town and spent a few hours wandering there. Back up to the fortress to try and get some night photos, but it started raining complete with lightening and thunder!
I kept second guessing myself and trying to decide if a full day was too much. I'm glad we stayed the whole day. Quite interesting. If you don't like castles or cute little shops, then it's not for you!