My latest project is a giant cat tree to take advantage of the high ceiling in our dining room. It stands over eight feet high so I refer to it as the cat sequoia. The top is secured to the window frame via a couple of eye hooks and beaded chain. In the picture below 4 out of our 5 cats are using it simultaneously. I didn't bother with a full Instructable as I was lazy in the documenting the building process and the construction concepts are pretty general. But I wanted to share, so hope you enjoy.