Great idea, I agree, i think less a bubble of safety, and more of a lore reason of ruins or something that implies some sort of lore implication would be really cool, for people that doesn't realize there is a story. Could be something simple you waking on the top of the ruins and the ladder/stairs is only one way ... aka falling down to get out. Or you are in a small tower/room and the door is one directional opening. So it's only safe till you leave/open up access to it.