Wildenstein
Wildenstein ("Wild Stone") was mentioned in documents for the first time in 1077, and a nearby monestary considered the castle as interlinked with their own scheme of defense to protect the area from insurgencies penetrating from the east. 

The Lords of Wildenstein took possession of the castle in the 12th Century, with the von Zimmern family taking possession up to the mid-1500s when they failed to have a male heir.  The Furstenberg family took over the castle in 1626 and held it until 1971, when they sold it to the German Youth Hostel Association.  Today, the castle houses a small restaurant and the Youth Hostel.
Above, a veiw of Wildenstein from across the Donau River valley.  Left and below, the main entrance to the castle.  The castle has a dry moat that protects the outer ward, and then the outer ward further protects the inner ward, with the same dry moat snaking its way around.  As a result, any attacker would have to fight his way through the moats and through the outer ward.  The photos show that this would be no mean feat.

All of these photos were taken in 2007.
The photo to the right shows part of the outer ward from the entrance to the inner ward.  The castle is built right into the living rock.

Below, a view of one of the turrets as part of the inner ward as seen from the courtyard.  The small loopholes allow the use of crossbows with a wide field of fire.

Bottom, a view of the courtyard where the restaurant is located.  Bottom right, a giant sized chess board for the folks who stay overnight at the castle.