Most of us know it already : there is a hidden dungeon under karazhan which can only be accessed by glitching and it is pretty damned scary.
(more information on it http://www.wowwiki.com/Crypt_%28Deadwind_Pass%29 )
Now this crypt has been around forever and when they revamped the world with cata they didn't remove it. Now my question is will they ever use it or delete it? What are your thoughts and speculations on it?