Like some other reviewers noted, I could hardly put it together with the cats in the way.  They love the cozy sleeping nests at the top, with both curling up in them on the floor as soon as they were unpacked. One refused to leave it, even as I lifted it into place for installation.  I noticed that some other reviewers said the sleeping areas were too small, but they seem fine for our two average size (13 to 15 lb.) cats.  We and they are all very happy with this purchase!