A transition structure for a tower comprises a plurality of panels that each includes a panel body having opposed upper and lower ends, a lower mounting surface at the lower end, an upper mounting surface at the upper end, and a pair of lateral mounting surfaces at lateral edges. The upper mounting surfaces are generally planar, and the panel bodies taper from their upper mounting surface to their lower mounting surface. Each panel is mounted to at least another of the panels at corresponding lateral surfaces to form, with the upper ends, the shape that conforms to the lower end of the tower to be supported. The transition structure also comprises a plurality of footings, each having an upper end mated to the lower mounting surface of one of the panels, a lower end configured to mate with a post of a foundation, and a footing body between the upper and lower ends.