We've built a special room for the cats in the backyard in our house, a sofa, some fitted out chairs, shelves with boxes on them, two low height windows, 3 doors with special openings, and an air conditioner unit for the excessive heat in the summer.
Bowls for dry food and water inside, wet food they can either catch by themselves or the leftovers of our food for change. The litter boxes are outside.
The only issue, they still prefer to sleep on top and under the cars, and on the chairs in the front yard to keep an eye on what we're doing.