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.
This is what the walls in Cat Heaven must look like! Covered in fabric mazes, easy to climb and easy to cling to. Tap the link for an awesome selection cat and kitten products for your feline companion!
DIY Cat Hacks - Cat Tree Wall Ikea Hack - Tips and Tricks Ideas for Cat Beds and Toys, Homemade Remedies for Fleas and Scratching - Do It Yourself Cat Treat Recips, Food and Gear for Your Pet - Cool Gifts for Cats
Cats Toys Ideas - Need a great cat door, but want something better than the standard flap? Here are 10 amazing and unique cat doors that you can buy or make yourself as a DIY cat door project. - Ideal toys for small cats