What is this castle?

I remember it being prominent in concept art but we never went there I don't think
http://i.imgur.com/JltHsVY.jpg

looks more like a Academy which would have probably been used for teaching young magic users into mastering Black magic.

Darth Vader's summer castle.

I have a theory that Dun Scaith might be turned into a housing ward. That castle could be the apartment.