Abstract: A self supporting roof structure comprises a plurality of vertically adjacent circular upwardly inwardly inclining at least partial rings stacked one on another. Each ring comprises a plurality of like horizontally adjacent panels each of which is an aliquot of the ring. Each panel comprises an outer surface which is convex from side to side, upwardly converging rectilinear sides, a concave top plate member, and a convex bottom plate member. The top and bottom plate members in each ring conform to respective upper and lower inwardly downwardly sloping conical surfaces of which the apex coincides with the axis of the roof structure. Preferably, at least one ring has a number of panels which is an integral number greater than one times the number of panels of the ring above.