I built a ring house all the way around the tops of one of those stone circles. It was a crescent for a while when I was branching from one to the other with core wood poles, but after I put in stone platforms around the top of each one and linked the in-between space with a couple of ironwood beams I was able to build a stone floor all the way around the top of the ring. It was pretty rad, and had enough space for all the kilns, smelters, and storage I needed. I walled off the ground level and put a small farm in the green space there for planting. Wish I had taken a picture, but it was on a friend's server that isn't up anymore.