We had a smaller cat tree to start with, but it is too short for the kittens to really stretch out on, but we made sure there was a space for it to sit in the larger one because they still like to play on it and use it as a stepping stool to get to the top. We put it next to the couch so we could watch them play, and they love running across the back of the couch onto the walkway. I'll explain how we built it in an article!
Blessed Be