I'm wondering if it would be feasible to build a retaining wall of vertical flagstone slabs. The walls would really just define a raised garden area; there is no slope to be "retained." They would be about two feet high, and the width of the garden area to be "retained" is only about two feet wide--it's a raised garden border around the perimeter of the yard. I think I could do this if I used the thinner, stand-up flagstone pieces, and sunk them about a foot. I could overlap them a little to avoid the vertical joints flexing outward over time. The top edge would be somewhat uneven, and a little sharp at first, but I think I could plant a ground cover like wooly thyme to soften it, which would grow down over it over time, as well. My question is, has anyone ever seen or heard of this being done? How did it work? How did it look? Any pictures? If you haven't heard of it, do you think it could be done?