Sneak a litter box into a comfy window seat, and it won't even feel like you're devoting any precious space to your cats, err, business. Tap the link for an awesome selection cat and kitten products for your feline companion!
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.
Litterbox cabinet - SUCH A GOOD IDEA! Give the cats their own little litter box cubby room. It gives them their privacy and you can contain any mess on the outside of the litter box and easily clean it up.
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.