Hohenurach
There are a number of castles in Germany that bear a similar name to the town they sit above, and Hohenurach is one of them.  Situated on a hill overlooking the town of Bad Urach and the Erms valley, Hohenurach was once a fairly good sized fortress, established by the Count of Urach in the mid-1000s.  First mentioned in documents in 1235, the castle became embroiled in a war between the Duke of Wurttemberg and that of Luxembourg, the same war that saw the demise of the Lichtenstein castle in 1310.  Hohenurach was also involved in the Thirty Years War, being occupied first by the Imperialist forces, and later by the Swedes under Bernard Saxe-Weimar.  By the 1760s, Duke Karl Eugen finally abandoned the castle as too expensive to maintain, and it gradually decayed to its present state.
Much has changed regarding Hohenurach in 30 years.  Up until 2007, my best photos of the castle came from the late 1970s.  I tried to visit in 2005, but a heavy rainstorm was closing in, and I had to cancel the hike.  But in 2007, I got a good chance to visit and it was well worth it.  Areas of the castle closed years ago are now open and worth seeing.  Above, the castle in 1979, and left in 2007 (as seen from Urach).  Below, two views of one of the battlements near the entrance (left in 2007, and right in 1979).
A number of underground or enclosed passages and battlements are now open to see.  One can feel how damp and cool life in a castle was, and considering the normally cool and damp climate of central Europe, one can see how uncomfortable such could become. 

To the left, one of the passages in 1979, and below left and right, passages in 2007.  The one on the right is the area below the entrance on the left in the photo above.
Left, the main entrance into the castle in 1979, which has changed little up to today.  After going through the entrance you must wind your way through a series of short tunnels to work your way into the inner ward of the castle (right, 2007).  As you wind your way progressively in, you encounter a number of enclosed fortified positions.