To prepare for our next kitty, a Maine Coon, I built this Kitty Condo extra heavy and extra sturdy. Maine Coons are big, heavy, and strong. We couldn't find any commercial products that seemed large enough or strong enough.
I started with plans I found on the internet, then doubled the base and bed materials. I extended the center shelf farther rearward to make it easier for our nearly 19-year-old year cat, Lucy, to make her way up to the second level bed. Also used more fasteners than the original plans called for.