One of my dreams when I win the Lottery is to build an indoor/outdoor kitty playland. Part would be indoors with places to climb and hide all the way up to the ceiling. Outdoor there will be kitty friendly plants, a fish pond were they could dream, places to roll in the warm sand, all the things our indoor kitties dream to do. Do a google seach and check out some of the set ups that are out there!!! $$$$$$$
Please don't think I'm saying that cats need to be outside animals. I'm not. Cats live much longer when they are kept indoors. All of mine are now indoor flea-lions, but there is still a natural urge for them to be the Kings (and Queens) of their jungles.