How were the columns at Carthage made?
A barrel of the diameter of the columns was used as a template. Once the column was rough cut to length from quarry stone, it was then formed into an octagonal shaped column, and then scraped down to the barrel size. This barrel was placed over one end and sand was added through holes in the barrel. Spinning the barrel would result in a smooth column, and as the column was sanded smooth and polished, the barrel was progressively moved along the column until the entire column was able to fit through the barrel. This is relatively easy to do, as marble is softer than the silica sand used for the final smoothing and polishing operation. All you really need is slave labor, and the Carthagenians weren’t short on that.
