Caerphilly Castle is an imposing medieval fortress mirrored in the waters of its placid lakes. It was built amid alarms and excursions by the lords of Glamorgan following their annexation of upland Senghenydd in 1267 and was completed by 1290. It was associated with a borough (NPRN 268017) and a vast deer park enclosing the Aber valley 3.0km to the north-west (NPRN 307764). The castle was in decline by the fifteenth century and it was ruinous by the earlier sixteenth. Nevertheless it was probably put into a state of defence in the mid seventeenth century when a great bastion or redoubt was raised to guard its north-western side (NPRN 300400). A major campaign of restoration and reconstruction was carried out in 1928-39. Since then the castle has been taken into state care and its lakes have been reflooded.
The castle consists of a great walled central court with tall round towers at each corner and huge twin-towered gatehouses on the east and west sides. Within is a magnificent earlier fourteenth century great hall and other grand apartments. The court is set within a concentric walled platform that rises from the waters of the lakes. These are held back by a massive fortified embankment on the east side that presents an unparalelled 280m long array of walls, towers and bastions towards the town. A corn mill is set within this area (NPRN 307852). There is a further walled platform on the west side of the castle.
Sources: RCAHMW Glamorgan Inventory III.1b The Later Castles (2000), 51-104
CADW Guide to Caerphilly Castle revised edition (1997)
John Wiles, RCAHMW, 5 February 2008