Keep a climbing route clear by considering the space above, below and beside every step, not just the visible platform surface. Remove ornaments, cables and other objects that could interfere with landing or turning. Check nearby doors, curtains and movable chairs, because a route can change during ordinary household activity. A cat should not need to weave through breakable items or depend on a drawer being left open.
If another piece of furniture forms part of the intended route, it must be stable and appropriate for that use; do not assume a decorative shelf can carry a jumping cat. Review the descent separately from the climb up, especially for a large or older cat. Keep cleaning access practical so clutter does not accumulate around the base. Once the arrangement is in use, watch for repeated detours or awkward pauses and adjust the environment rather than expecting the cat to work around obstacles.
Recheck the route with curtains drawn and cupboards or room doors in their normal positions. A clear route in a product photo can become obstructed later by a curtain, chair back or item placed temporarily on a landing surface.
For product comparisons alongside this advice, see Ultimate PawHouse and Taj-MeowHall. The details below explain their sizes and uses.
Further reading: cats.org.uk; rspca.org.uk.
Ultimate PawHouse
Taj-MeowHall
Cat-Cave