The column terra cotta are likely some sort of drain pipe for in ground use. We have a brick yard near here that has numerous shapes of drain pipe such as that, that turned on the end could be used for pottery, except that the bottom is open. It is not uncommon to use the really wide ones (12" and greater) as large permanent planters. I know of one being used about 1/2 mile from where I live. It's probably about 2' wide.