The Castle is the thing in this place, it is historical place that is now used as a youth hostel. It is at the top on the cliff, many stairs to climb up and even your car will work hard to get to the top.
Depends on the season and the weather of course how you are going to enjoy the forest, we had a cloudy day, a bit foggy as you can see from this picture, but it was actually not bad at all as it was not too hot to take a long walk without sweating too much.
I am not sure that this is a must see, but as I assume that you will stay here overnight at the castle, I am recommending to take a walk at the forest around. Just walk up the mountain from the castle, there is a mark road, it will not take you too long to make the loop and come back to where you started.