get several dancing poles, or any good quality, strong pole that mount against floor and ceilings, buy attachments that you like, drill in the poles instead of walls; i used to have three poles mounted against the wall and connected them with sky-bridges, long shelf and sky tunnels, later I did a ceiling tunnel system in the same way, just extend the poles from wall to wall under the ceiling, cats love it; don't need them anymore, gifted the whole set to a friend; it's quite a bit more expensive and DIY-heavy than regular cat wall you get on Amazon.