Abstract: A high, self-supporting smokestack or tower having a structure constructed by stacking precast reinforced concrete sections one upon the other, the cross-sectional area of the structure being larger at the bottom than at the top and concentrated reinforcement being provided along the length of the structure to bear the horizontal forces acting upon the smokestack or tower. The structure exhibits ribs provided with concentrated reinforcement and extending longitudinally on the outside of the structure at least along its lower portion, the radial extent of these ribs increasing from the top to the bottom at least so as to correspond essentially to the bending moment progression resulting from the horizontal stress. A mould device for producing precast reinforced concrete parts for such smokestacks or towers, in which mould sections are provided which are radially adjustable for fashioning the front surfaces of the ribs.