i put up about 20 cat stairs/platforms on the inside of my apartment, along a whole wall and wrapping around my breakfast nook, comprised of 4 main paths and 3 different entry points. there are 2 cat beds, a cat grass planter, and 2 sunning platforms incorporated. it was a fun project and my cat (and former cats) loves it! when she gets the zoomies, she'll do laps up and down the stairs out to the other room and back.

i should note that these swiss cat ladders were a partial inspiration, having run across a similar article a few years ago.