Feline Furniture Cat Castle. WOW! Are you looking for a very customizable, very configurable cat furniture set? This modular cat activity center is called the Cat Castle and rightly so. The Cat Castle is a build-to-suit your decor type cat furniture that lets you shape it any way you wish while allowing your cats to have hours of entertainment and exercise. There are cat condos and hammocks in random areas to provide plenty of resting and playing places for your cats. $500.