I love this, and more importantly, my cat is freaking out for it. She has so much fun running through it and playing on the lower level and then sleeping on the top. She's on it 24-7. It's extremely sturdy and strong - I've put all of my weight on it and it supported me. The only reason I didn't give it 5 stars is because it smelled a little mildewy when it arrived and took time to air out and the smell to go away.