A basement in a dream often represents what sits below ordinary awareness -- old fears, buried memories, or feelings you've stored away rather than dealt with. Discovering a room down there you didn't know existed can mirror the surprise of uncovering something in yourself you'd forgotten was still present.
He that would truly promote Art must insist as much on the confutation of false opinions delivered by others, as in the declaration or truth. - Cardan Girolamo (1501-1576)