Safe Outdoor Cat Enclosures
It is possible to create safe outdoor enclosures for your cats. However, the greatest possible care must be taken to ensure that (1) the cats cannot get out and (2) predators cannot get in.
Click here for more info: www.pets-haven.com/cat_outdoor_enclosure.htm
Check out an enclosed back yard
Check out Beautiful World Living Environments
Below are two photographs of a custom-built safe outdoor extension:

