The largest castle in Wales and the second largest in Britain — a masterpiece of 13th-century concentric castle design with revolutionary water defences.
Caerphilly Castle is the largest castle in Wales and the second largest castle in Britain after Windsor, covering over 30 acres. Built by the Anglo-Norman lord Gilbert de Clare between 1268 and 1271 and substantially enlarged by his son over subsequent decades, Caerphilly represents the most advanced castle-building of the thirteenth century, combining a concentric defensive plan with an extraordinary system of artificial lakes that formed an integrated part of the fortifications.
The castle occupies an island created by damming local streams, surrounded by an outer moat and a larger outer lake. Its concentric plan — an outer ring of walls and towers enclosing a stronger inner ward — meant that attackers who breached the outer defences found themselves in a killing ground between two defended circuits. The great hall and residential apartments are among the finest surviving examples of high medieval domestic architecture in Wales. The castle successfully resisted Llywelyn ap Gruffudd's siege in 1270–71, demonstrating the effectiveness of its revolutionary design. The south-east tower leans at an angle greater than the Tower of Pisa — the result of an attempted demolition during the Civil War.
The most technically sophisticated medieval castle in Wales, Caerphilly is a landmark in the development of English and Welsh castle-building, pioneering the concentric plan and water-defence integration that influenced castle construction across Britain and France.
Built by Gilbert de Clare to assert control over Glamorgan against the Welsh prince Llywelyn ap Gruffudd. Revolutionary water defences and early concentric plan.
Further work by Gilbert the Red and subsequent owners. The outer enclosure, water defences, and great hall elaborated to their current form.
The castle plays a major role in the downfall of Edward II. Seized by Mortimer; later by Owain Glyndŵr's rebels.
Slighting (deliberate damage) carried out. The south-east tower left leaning at a dramatic angle as a result of an attempt to demolish it.
The leaning south-east tower — the result of Civil War demolition attempts, leaning at 10 degrees from vertical
Lead statues of Edward I and his heirs, originally decorating the walls and now on display in the castle
Extensive medieval stonework including the great hall, inner ward, and gatehouse towers among the best-preserved in Wales
Evidence of a water mill built into the dam that created the castle's defensive lakes
A lead plaque commemorating its construction by Gilbert de Clare
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