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.
This climbing structure leads to two catwalks. The whole assembly is known as Kitty City. Photo by Marjorie Darrow and Ryan Davis Tap the link for an awesome selection cat and kitten products for your feline companion!
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.