I have four cats ranging in age from 7 years to 8 months (2, brother  sister) and the baby at 10 weeks.  I researched cat trees everywhere and was looking for one that would be stable, with the house on the bottom it is very stable.  My cats were playing in and on it as we were putting it together, which was very simple.  I especially like that the house has two entries and a peek hole in the top, lots of fun for all.  They all made it to the penthouse the first day.  They take turns sleeping on it (or whichever level they choose).  Just cant say enough good.  Wish I had another but dont  have room.  I have it in front of a window which is also a good spot as they all like to look out.  Thanks for a great product!!!!