Every full-time indoor cat should have a window box (at least)

Classy cat window box. From Catio Spaces
Please watch the entire video as there is a nice surprise ending. This large window box catio is cute. It is a perfect way to give a full-time indoor cat some fresh air and the chance to smell the smells of nature and hear its sounds. It won’t work for all properties but for many it will. It’s probably quite inexpensive so there is no excuse for not getting a decent carpenter (the hard part is finding one) to construct a mini-catio or DIY.
https://twitter.com/i/status/1089174920096088065
I see photographs of cat window boxes quite often and they are always from America. I never see this sort of construction in the UK, which is a shame. The reason is probably because the vast majority of cat guardians in the UK let their cats go outside and wander.
For many homes in densely populated England keeping a cat inside and adding to the facilities with a mini-catio is the best way to care for your cat. Safety first must be the rule but it is not always applied in the UK.
I have just come back from a walk down by the river and before I had gone 30 yards I saw a lost cat poster on a lamppost. I see them not infrequently.
The American business Cat Spaces (located in Edmonds, Washington I believe) have catio plans for sale which is interesting. They say they are DIY catios. You buy the plans for upwards of $70 and the do it yourself (or hire a carpenter, if needs must).