Apparently, "Catios" are a thing now. A Catio is basically a screened-in area where cats can experience the outdoors and still be safe indoors. (In other words, a cat's patio.) I wonder though why you would build such a retreat just for your cats and not also for you and your fellow humans to enjoy as well?
One of the first addition I put on my house when I moved in almost 15 years ago was a screened-in sun room. It is unheated, so I only open up the kitchen door to it when the weather gets about 60 degrees -- usually from about April to October. I don't use air-conditioning, so the sun room's open windows are a vital part of my house's air-flow in the heat of summer. It is also where I hang my laundry to dry each week -- a very convenient way to have fresh, crisp towels and sheets in the city and not have them out in the elements or letting my undergarments be exposed to my neighborhoods' prying eyes. The sun room is also where I collect, dry, and save seeds from my garden as well cure my garden harvests such as garlic and sweet potatoes. Of course, I also use it for relaxing on a summer evening free from annoying mosquitoes and a place for having guests over to chat and relax.
For my cats though, it is Xanadu. They run to the door out to the sun room when I come down to make breakfast in the morning and they spend practically the whole day in there watching my water garden out one side window and all the rest of the gardens through the other two sides of the sun room. It provides a panoramic view on an endless parade of bird visitors, flying insects, and other wildlife that keeps them absorbed all day. Before I go to bed each night, I have to kick the cats out of this paradise and lock up. They don't object too badly, but occasionally, Santino, my big Maine Coon, throws a fit and refuses to come "in." If I let him, he'd live out there 24-7 hours a day, 365 days a year.
Do you have an indoor/outdoor area that you and your cats enjoy together?
Here is the Country Living article on the catios trend:
http://www.countryliving.com/life/kids-pets/a35760/catios-trend/?src=spr_FBPAGE&spr_id=1453_200226585
(Image from Pinterest.com -- uncredited -- source being sought.)