 Here's my cats playing on their homemade cat tree. You can see it's constructed out of cardboard, tinfoil, duct tape, hot glue. Basically they've got two little balcony things, each sometimes equipped with a toy. On the inside there's a series of shelves and stuff that they can jump up on. And then they can crawl up through the top here and then they can find themselves perching on the top. One of them is not in there anymore. But here's the little balcony thing on the other side. You can see it's built out of reinforced cardboard. It's actually quite strong and can easily support one of these little kittens.