The recommended dimensions for a catio depend on the number of cats and their activity levels. For a single cat, a minimum of 2 feet by 4 feet is suggested, allowing vertical space for climbing and perching. For multiple cats, aim for at least 2 square feet per cat, with ample vertical and horizontal space to prevent territorial disputes. Including shelves, towers, and hiding spots can enhance the environment. Customizing the catio to fit available space while ensuring it is safe, secure, and enriching will benefit all feline inhabitants.