Giaguara describes, and I agree: Cat room. This would be awesome. To be then connected to a catio, and a small snuggly corner with bookshelves where the humans and cats could have some proper snuggly time.
The wall cat wheel // the wall bike for cats by HolinDesign
5 DIY Cat Play Spaces For very little money, you can create simple and fun playscapes for your cat. get some yourself some pawtastic adorable cat shirts, cat socks, and other cat apparel by tapping the pin!