User blog comment:TombRaiser/Dragonborn: Hidden Landmarks/@comment-3492791-20121217044523/@comment-3492791-20121219234103

Hence why most dungeons have locked gates at the end to prevent entering from the wrong side. I, being such a devious rascal, can personally attest to there being some dungeons that can be entered from the wrong direction, but for the most part they prevent it by using one way doors.