I suppose you'll have to contact the castle (see website) for information. Probably won't be cheap though!
Address: Schlossstr 36, 56812 Cochem
Directions: Take a shuttle bus from the parking lot near the train station or do the steep climb (about 15 minutes) on foot. If by car: drive west along the Mosel, then turn right into Schlossstrasse. But beware: only about 20 places for parking!


