Level 0 is most likely the first level you will encounter in the Backrooms. Apart from very rare instances, most rooms contain nothing but the stink of old moist carpet, the madness of mono-yellow and the endless background noise of fluorescent lights at maximum hum-buzz. Level 0 is approximately 600 million square miles large.
Although level 0 is mostly made up of randomly segmented rooms, hallways; flights of stairs; and wide, open areas can be found occasionally. It is by far the safest level. Beings can be found lurking around here, albeit incredibly rarely.