Ok, I suppose the castle density in the southern half of Germany is higher than anywhere else in the world, except maybe Scotland. Look up
www.burgtour.de for a very incomplete and regionally biased list of castles, ruins and remains.
For my first years, I spent every vacation with my grandparents climbing up and down Windeck Castle in Weinheim/Bergstrasse.
Today, I know Windeck is nothing special at all, but in my youth this ruin was every story of Knights and heroism and so. I suppose today's parents would get hysterical when their children would climb the same walls and go down the same dungeons I did, even though it was only around 1985.
But the drei Gleichen is simply a magnificent sight, even from the Autobahn.
First time I saw them it was enroute to Berlin, on a sunny January morning with snow.