For two cats, i would do this spuble long and keep it umder a window sill, drill some holes in the back so it can air out, keep both sides totally separate so the cats can have their own space but also keep everything together for cleaning purposes.
Minimalist IKEA Cabinet Hack, and lots of other ideas on hiding a litter box. Not just for the litter box but for a dog's or cat's pet bed, when company is over or just during the day, just shut the door and it won't have to be seen until bedtime.
I am thinking I need to put a wood exterior on the cat cage then build two of these boxes on top, one for litter and one for food/water. Tap the link Now - Luxury Cat Gear - Up to off and Free Worldwide Shipping! Check out our Cat