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!