Rheinstein / Reichenstein
A forboding picture of Reichenstein during the late winter of early 1979 (left).  This castle is located by the town of Trechtingshausen, and was started in the 1000s.  Twice in the 1200s the castle was destroyed, once by a league of Rhein towns, the other by the Holy Roman Emperor Rudolf von Habsburg.  It was renovated in the early 1900s.

Reichenstein's construction shows the nature of castles built before the development of cannon and artillery, in that it has high curtain walls to thwart efforts to storm the walls.

Below, two views (left 1979, right 2005) of the main entrance. 
Left, looking up at one of the great towers.  Today, Reichenstein has a nice little restaurant in it (as do many other castles), and of course, a full tour.  If you're into tours, great.  As for me, I prefer to wander the structure and let myself get swept back hundreds of years.
Left, a nice view northward along the Rhein valley with Reichenstein across the river.

Below, two close views of the castle from the east side of the river.  The large curtain walls, impractical against more modern seige cannon, are clearly visible.
Left and below left, two views of Reichenstein in 2007.  The one on the left was taken from the camping ground, while the one below was taken with a telephoto lens from a cruise boat.