Regarding adaptive re-use for roundhouses: Not a full roundhouse, but the old enginehouse in Dover NH has been the home of Salmon Falls Pottery for many years. My wife likes to shop there for pottery whenever we're in the area, and customers can watch the potters at work. It's quite fascinating to see the artisans take lumps of clay and turn them into useful and/or decorative items. And there's a relatively busy Pan Am (formerly Guilford, and before that Boston & Maine) railroad nearby.