Starting off we have the Parking Structure, Ground Floor. a 17 1/2" by 17 1/2" footprint, serving as the base for what can be structure as large as your wallet can afford. At a minimum all you need is the ground floor and the top floor, however it would seem a pity to not at least get one middle floor. Each level runs $19.80 USD and is laser cut MDF.
From top left...Ground Floor, Top Floor, Ground & Top Floor, Middle Floor. What is pictured is the 15mm version the 28mm version is identical simply larger.