Jon is going to work on interiors and I will think about the grounds etc...
I immediately thought of 3 well-known Castles
1. Neuschwanstein (Disney modelled their Castles on this one and it was used in "Chitty-Chitty Bang Bang") I love the tower on the right...

2. The Castle from "Where Eagles Dare" - (Remember the music?)


Impenetrable rock only reached by cable car...

3. And then Castle Wolfenstein...

Horrors can lurk in the Castle basement...


So far I see a rock, perhaps on a river Island, Castle on top, courtyard in middle, perhaps obligatory radio room with music playing near the alarm switch, but also dungeons with horrors lurking, "Secret" stone doors etc... towers with good sniping, some caves from the river area inside the rock into the Castle... a pulley and basket lift, like in "Name of the Rose" or "You only live twice". A giant main hall, with a feast laid out, fireplaces which require further investigation...perhaps a cable car, a few drainpipes etc...
Any ideas?