Furstenberg
As you leave Trechtingshausen and head north along the west bank of the river, you come across Furstenberg, above the small village of Rheindiebach.

The two views here are actually from the east bank.  Right, 2005, and below in 1978.
Furstenberg clings to the corner of two slopes, one facing the Rhein and the other facing a small valley that pushes westward.  The castle is a ruin, but is currently undergoing some restoration, apparently to keep it from falling apart.  The tower unfortunately is closed.

The best place to park is in the lot of a small cemetary in Ober-Diebach, just up the road from the river.  The walk up is easy, amidst the vineyards with the castle beyond.
A good view of Furstenberg as seen from Nollig on the other side of the Rhein.  The hillside curtain wall can be more clearly seen, and how it helped protect the inner ward against missile attack from above.