Symbolize our unconscious. If it is clean and organized, then it indicates that our inner world is rich and organized. If it is dirty, messy and full of useless junk, then we will find our unconscious as well. If it is well-stocked, then it represents joy and gladness.
Dream dictionary: Basement, cellar dream meanings
…Dreaming that you are in a basement, foretells that you will see prosperous opportunities abating, and with them, pleasure will dwindle into trouble and care. See Cellar….