I should add that any shelves will do. Most of my shelf units have one empty shelf for the cats. I have one small shelf with hearts cut out and Mr. Spunky loves to put his head through it to attack me. He is precious. Never have the camera ready.

In the early days I had put bells on ribbons under chairs for the cats to play. The chair (Old-fashioned ladderback) serves as a hidey hole and the bell makes noise. The bell was big enough so they couldn't swallow it (I also have no other pets or kids).