Saarburg
One of the smaller towers showing extant authentic architecture to the doorway.  It appears that this entrance was attached to an upper section no longer extant.

Below, the entrance into the main watch tower.
Below, naturally the wooden stairs are of recent origin.  However, they do capture the essence of what the stairs would have been like back then. 
Right and below, two views from the watch tower looking down into the entrance to the palas.  It is possible that the cement and mortar has covered up any evidence of floor supports, but examination of the walls implies that the entrance was actually a large high ceilinged affair designed to impress any visitors.
Left, a view of the courtyard from the watch tower.  The bridge across the Saar River is visible to the left, and also in the photo below.


Bottom, two photos showing barge traffic on the river and the town of Saarburg.