If you're not careful and you suffocate in gravel and fall through the world in a cave, you'll end up in the Minerooms, where it's nothing but the stink of old moist carpet, the madness of endstone and sandstone, the endless background noise of sea lanterns at maximum hum-buzz, and approximately 1553992866 blocks of randomly segmented, empty rooms to be trapped in.

Notch save you if you hear an entity wandering around nearby, because it sure as Nether has heard you.