9 Of The Most Impregnable Castles In FictionRob Bricken4/28/15 1:30pm30925EditInvite manuallyPromoteDismissUndismissHideGo to permalinkWhat makes a castle impregnable? Is it the walls? Its inhabitants? Other defenses? A combination of all of the above? All we can tell you is this — no one is pregnating these nine fictional castles any time soon.