A window perch can complement a climbing tower when it provides a different useful place to rest or observe the room and outdoors. It does not need to be connected to the tower, and any intended route between them must be stable and suitable for the cat. Check the perch's own capacity, usable dimensions and installation instructions independently; a secure tower does not make an unsuitable window attachment safer.
Consider sunlight and temperature changes, as a popular morning spot may become uncomfortable later. Manage windows and blind cords so the new position does not introduce an escape or entanglement risk. In a multi-cat home, separate access can make the additional perch more helpful than another bed on the same tower. Watch your cat's response to the view too. If outdoor animals cause repeated agitation, offer a resting place with a calmer outlook rather than assuming every window is enriching.
Think of the two pieces as separate destinations unless a properly supported connection is expressly suitable. The cat should be able to leave the window perch even when another cat occupies the tower’s nearest platform.
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