Finally, after much searching (for someone to build one) and researching (including building codes, city zoning and fire requirements) I was able to get a catio built.
But Sabastion, Noodles, and, of course, Pumpkin love to go out into the secure area and climb onto the perches to catch the sun or to climb around under the bushes to explore. I love to see them enjoy their new extension to their home.
As far as city codes, I had to have the catio no closer than 15 feet from the edge of my property line and had to make it under 120 square feet to meet fire code. It may be different for your neighborhood. I installed a custom made window that has a cat door in it so they can come and go into the catio. Also, I had a locking door knob (as I have a full screen door installed in it) that locks automatically from the outside, but is always unlocked from the inside in the case that I have to use that bedroom window as a fire exit.
The Audobon Society promotes catios. In other cities, Austin and Portland, as well as others, I believe. They have yearly catio tours where people can go and view catios around town that people have made. The Audobon Society encourages catios because roaming outdoor cats are decimating city bird populations. Catios allow cats the enjoyment of the outdoors, while keeping the cats safe from cars, predators and other dangers, they protect the bird population and help to prevent the spread of disease from cats encountering other cats or wildlife.
I would like to encourage anyone who has cats to consider installing a catio. It doesn't have to be as large as the one here, some are simple window boxes. My cats love it and I am happy I was able to fulfill my promise to Pumpkin (and to myself).