I have had a closer look and it may in fact be 2 floors, I have used the top picture you posted Locutusofbored and I have added highlights to show the floors (amateurish using paint I know).
I should have made the writing bigger as well but you get the idea. If you save it to PC and then zoom in you can see it clearly.
Still disagree. Looks to me like a single corridor with enough room for one above and two below.