This structures has at least two phases and was undoubtedly used for ironworking. Initially thought to be a blacksmith forge, now archaeologists are not so sure. A blacksmith would have been needed to shoe horses and repair tool and mine tubs. However, no hammer scale (usual by-product of blacksmithing) was identified and surprisingly a high amount of slag was identified. Slag is a waste product of ironmaking, usually associated with bloomeries and blast furnaces. A hearth for heating (with slot of doors) and storage can be seen; as can a smooth work surface.