Schmidtberg
When you first hike down the trail and see Schmidtberg, you get this impression you are gazing out across a valley to ancient Inca ruins.  The photos here, taken in 2008, simply don't do the view justice.

Notice that to the upper right on the distant hill are some structures.  These belong to a restored Celtic village.  While such restorations can be interesting, I simply didn't have the time to see it and so never got there.  Perhaps on another trip?
Below, left and right.  Two views of  Schmidtberg, left in 1977 and right around 2005.  These photos come from the historical display board posted at the ruins, and view the ruins from opposite directions.  Some rebuilding and restoration work has been done since 1977.
To the right, a set of carved stairs leading up to the palas area of the castle.  These stairs appear to be authentic without much restoration work.
Left, the causeway to the main entrance.  This spans a dry moat and would have had a bastion on the side opposite the main castle to protect it.
Schmidtberg was started as early as 926, making it the oldest extant castle in the Hinsruck region and one of the oldest in Germany.  By the the 1100s, the castle was known as Smedeburg, an obvious early etymological precurser of its current name.  It also was designed with an upper and lower castle, though the latter appears to have vanished in history.  By the 1400s the castle came under the ownership of the Archbishop of Trier.  In 1688, during the War of the Palatinate Succession, the castle was besieged and destroyed by French troops.  During the 1970s the castle received some restoration work to stop the decay of the remains.