The Double-Helix Cat Towers are an example of creative, artistic re-use of waste cardboard.  Thick dual-ply cardboard used to ship solar panels across the Atlantic was re-used to create a helical structure 1.5" at a time with pieces cut from laminated cardboard sheet-goods using 6 layers of cardboard, each.  When you see a cat using the tower, either perched high up or just digging their claws in deeply, you can see they like it.  They like it a lot!