Even the DIY projects I came across were consistently awful (except Bob Walker's work in his book "The Cats'House" -- not my taste, but beautifully done). As one who tends to seek the simplest, most integrated solutions to any design problem, the notion of floating shelves seemed a likely answer. These are a combination of 12” and 36” units, purchased at West Elm and Home Depot,respectively, and carpeted with Flor tiles (http://www.interfaceflor.com) using industrial glue. The smaller shelves needed stronger attachment hardware to handle the weight. Note: for experimenting kittens, be sure to seal the edges of cut carpeting by carefully melting them with a flame – certain industrial fibers can cut up feline insides. And as you can see, the boys love their platforms!