I belong to a water gardening society here. For our display at the current lawn and garden show, we built a "myan Temple" (step pyramid) with a wooden structure covered in styrofoam sheets. The styrofoam was treated with acetone and paint thinner to give it the appearence of worn stone. Then spray painted natural stone colors.It looks great. I have a chance of getting some blocks of styrofoam aprox. 18 inches thick. Has anyone used or seen anything like this used in home gardens. I am going to try it, but I'm wondering how it will be effected by our midwest weather.