Bunny Castle - home improvement stores might have cut offs or odd sized pieces of wood. Take what you can get for cheap, and build an edible castle. Top with carpet pieces or in this case, felt for grip.
36 Awesone Recycled Wine Barrel Ideas http://theownerbuildernetwork.co/byl6 There are many ways of re-purposing wine barrels, here are some of the best ideas that we’ve come across… Which of these ideas do you like best?
"A Cat gym for chubby paws and swinging bellies: Run, Kitty. Run! If your indoor cats are putting on a little extra weight, you could try getting them into this running wheel. It’s highly unlikely 15-pound Tigger will take to it but some of his slimmer siblings might. Every little bit counts."