I've actually been to a castle in Heidelberg..

When I was a little kid.. All my relatives are in Germany and we travel all over Germany a couple of times when I was a little kid.. Visited several castles, but would have to find my scrapbook to figure out which ones.. I do specifically remember Heidelberg, tho.. It might be the castle you speak of.. If I find my scrapbook, I'll shoot a pic of the postcards I have from there..