No, I know nothing about the castle except that I walked through the area and stopped to look. I think it is normally open for visitors but was shut on the day I was there. It sure made for a good subject to photograph though!
I visited Hardegg as part of a walking trip through the forests from the Czech side. It was beautiful even on a cold overcast day - very moody. We have no architecture or scenery like this at home, so I soaked it up with great enthusiasm! Thanks for the comments