It looks cool, no doubt about it. From an engineering / strength of materials standpoint there's no way you could get something built up from individual stones to hang together when cantilevered like that. Stone buildings' strength is mostly vertical, flying buttresses notwithstanding. BUT you do see natural rock formations vaguely like that - differentially eroded layers, or big-on-little. The more monolithic (ha: literally "one rock") it is the better I would thing it would stand. Could it be a single pillar hollowed out and notched? Maybe your people LIKE the aesthetic of built-up stonework, so they carve the outside to look more like many pieces went into it?