The ruins of a corn mill are situated on the great dam embankment on the eastern side of the colossal castle of Caerphilly (NPRN 94497).
The mill is thought to have been built as part of the first period of construction in 1268-71 and would have been working soon after 1272 when the waters had risen to fill the great south lake. It was reputedly working until the seventeenth century, making it one of the last funtioning parts of the castle. It is a low, stoutly built stone-walled building consisting of a deep wheelpit that housed either an overshot or an undershot wheel, with an overflow channel to one side and the machine room on the other.

Sources: RCAHMW Glamorgan Inventory III.1b The Later Castles (2000), 95; CADW Guide to Caerphilly Castle revised edition (1997), 31-2; Jones G.G., The Corn Mills of Caerphilly and the Surrounding District, in Melin: the Journal of the Welsh Mills Society, vol. 10 (1994), pp43-73.

John Wiles, RCAHMW, 05.02.2008.