Start from the one fact that shapes everything: the height outside
Nine floors up, vertical space is a gift indoors and a hazard outdoors, so this apartment's climbing plan splits cleanly in two. Inside, height is pure enrichment — shelves, tall furniture and perches that let the cat cross the room above the floor. Outside, the balcony only joins the route once it is enclosed with properly fixed, floor-to-ceiling mesh or netting rated for a cat's weight and claws, because a cat chasing a pigeon through a railing gap at that height has no second chance. Decide that boundary first, and design every indoor route to reward staying in.
Building the indoor circuit
Begin with a tall scratching post, at least chest height and heavy or bracketed so it never rocks, placed where the cat already likes to stand and survey. From its top, a wall shelf leads to the top of a bookcase, then a second shelf steps down to a deep window perch at the opposite end, giving a full circuit with two directions of travel so the cat never has to reverse past a rival or a startled human. Space the steps so a normal stride and jump covers each gap, line landing surfaces with a grippy mat or carpet offcut, and anchor every shelf into studs or solid fixings — a shelf that flexes once will be refused for months.
The balcony, converted rather than banned
A flat ban wastes the apartment's best view and fresh air, and many cats will keep lobbying at the door. The workable compromise is full enclosure: mesh panels fixed to the balcony frame on every open side and across the top if the design allows climbing that high, checked at each corner for gaps a head could push through. Inside that enclosure, one sturdy perch at railing height becomes the cat's lookout over the city. Until the enclosure is finished and inspected, the balcony door stays closed during the cat's active hours — partial fixes, like a single screen door, do not survive a determined cat.
Furniture reality in a rented-feeling city flat
Apartment vertical space often has to coexist with limited floor area and a landlord's rules about drilling. Where wall fixings are restricted, lean on freestanding height instead: a tall bookcase used as a climbing tower with shelves cleared in a zig-zag, a wardrobe-top bed reached from a chest of drawers, and tension-mounted posts that brace between floor and ceiling without screws. Keep the floor footprint small by building over existing furniture rather than adding a bulky cat tree in the middle of the room, and keep one descent route that does not require jumping onto the dining table, or every meal becomes a negotiation.
Keeping the high route trustworthy over time
Shelves loosen, mesh gets clawed, and a route that felt solid in month one can wobble by month four, which matters far more at nine floors than at ground level. Build a simple habit of a weekly once-over: tug each shelf, run a hand along the balcony mesh edges, and check the tall post's base for rocking. Putting that inspection on KinsLe Care Teams, with the task marked complete and timestamped each week, means the high-rise checks happen on schedule even in a busy week, and everyone can see the route was verified rather than assumed.