I know they were inhabited by the ancient Ayleids, etc, but in Morrowind you had Dwemer Ruins which were clearly factories, and with Oblivion I have no idea what the ruins are. Occasionally they call them tombs, which I guess makes sense, but they can't all be tombs, can they? They're not exactly inhabitable, because of the traps everywhere, so what are they?
My best guess right now is that they're prisons, because the things that hang from the ceilings in some rooms look a lot like cells - and putting huge traps everywhere would make a lot of sense. Thoughts?