we have on of this big plastic boxes as a litter box for a while and it's a great idea... cats love it as they have more space and we don't have to worry about not cleaning when we are away.

Actually we have a tall one, about 35cm tall I think, and it's great- the cats love thier privacy inside and also they don't throw kitty litter out so it's much cleaner...in the other boes we have they tend to dig next to the door and a lot of litter will fly out of there...