The Castle of Veliki Tabor is worth the trip, for example you start in Zagreb go to the Spas, further on the way you pass Kumrovec, worth a short walk between the old buildings. The trip to Veliki Tabor is on small roads in the hills. For the moment (april 2015) the castle is being restored inside. Only half of the site is accesible for the moment. The manager however was very friendly and let me have a quick look on the other part.
See the pictures in the link to have an impression of the castle itself and the museum part inside.
