When we bought our house the only way to get from the main level to the walk out level was a cast iron circular stair case. I always thought they were sort of nifty, and a huge space saver. I would soon discover that they are also extremely unfunctional. You can’t take your garbage out, or carry your laundry to the bedroom very easily using the contraption. I would eventually take them out of our house and figure out how to put a set of real stairs in our place. So if they sound like a good idea to you my advice is save your money. Circular stairs = bad idea.