The incline support tower with its enigmatic archway in the base. The archway forms what appears to be either a hearth or flue exit. It has been suggested that it was once a blast furnace or a lime kiln. However, it was built at the time of the incline itself and how it could have functioned as such is very much open to conjecture given its location relative to other adjacent structures.
Photograph © Crown copyright: Royal Commission on the Ancient and Historical Monuments of Wales