For some reason, bathroom mats that have a rubberized bottom can become a place for urinating. BOX A cat has a right to a clean and convenient litter box that can be used with privacy. Each cat should have its own, although in the end they probably will use one another's boxes. Whether you use the cheapest clay litter or the clumping kind, choose a litter box with care. It should have a ridge around the top to reduce tracking, and until you know a cat well and are willing to take a chance, forget the covered litter boxes.
Many cats simply refuse to go inside the closed quarters.
Anyone who hides a litter box so that neighbors won't see how seldom it is cleaned has started a timebomb. At some point, the cat will refuse to use it. The kind of litter used may be a factor. For kittens, the best choice of all is the cheap kitty litter clay at the supermarket. Or having one's entire environment removed into cardboard boxes and taken away, piece by piece.