We have 2 cats. One of them loves to climb to the top tier and lie there looking down on everyone and everything while we sit in the family room watching TV. She's about 10 pounds, and when she scampers to the top tier the tower wobbles a little bit (but has never come close to tipping over); it is stable otherwise, even while she plays with the hanging toy. She also goes in the hideout hole sometimes, and seems to appreciate the wide, cord-covered posts for scratching. Our other cat, who is about 16 pounds, has investigated the hole, but I think he's unsure about how to get in or if he will fit (although he clearly would). Other than that, he basically ignores it. We like it, and at least one of our cats likes it... maybe the other fella will come around!