12" Round, Smooth, Wood, Non-Tapered Column. We include the Base and Capitol that have a footprint of 14" square. The base and capitol and the column shaft sits in between. This column may be split, at extra cost, to make two pilasters or to wrap around jack post or support. The inside diameter is about 10". Interior Columns, Wind Turbine, Tapered, Smooth, Lamp, Structures, Round, Footprint