The 10 strongest castles in Wales

Edward I's imperial statement in stone: polygonal towers and banded masonry consciously echoing the walls of Constantinople, the towering Eagle Tower, and a curtain bound into the walled town on a peninsula between the River Seiont and the Menai Strait, so it could always be resupplied from the sea.

Its record is honest rather than spotless. In 1294 the still-unfinished castle, defended only by timber ramparts, was overrun when Madog ap Llywelyn's revolt seized the town; Edward retook it in 1295. Once complete it proved its strength, twice besieged by Owain Glyndŵr's forces, with French support, in 1403 and 1404, and it held both times, though the town outside its walls was burned.

Eight massive drum towers and a high curtain riding a long spine of rock above the estuary, divided into inner and outer wards and closed at each end by a barbican, the whole circuit tied into the town walls. The bedrock made mining or undermining all but impossible, and the sea kept it supplied.

It was never stormed, but it was famously lost by a trick. On Good Friday 1401 Rhys and Gwilym ap Tudur, cousins of Glyndŵr, slipped inside disguised as carpenters while most of the garrison was at church in the town, killed the watch, and held the castle for roughly three months before negotiating a pardon.

The largest castle in Wales and one of the greatest medieval fortifications in Britain: Gilbert de Clare's pioneering concentric design of the 1270s, walls within walls, ringed by vast artificial lakes and dams that held any attacker's siege engines back beyond effective range. Its eastern gatehouse and water-defence platform form one of the most sophisticated defensive systems of the age.

That scale told in war. In 1326-27 a garrison under Sir John de Felton held out for months against William la Zouche's besieging army, surrendering only on terms in March 1327. Earlier Welsh assaults, by Llywelyn ap Gruffudd in 1270 and Llywelyn Bren in 1316, had failed to take it.

The most technically perfect concentric castle ever attempted, four near-symmetrical rings of defence, a low outer wall bristling with towers inside a water-filled moat fed by its own tidal dock, and inner gatehouses that could be raked by fire from every side. Arnold Taylor called it Britain's most perfect example of symmetrical concentric planning.

On paper it is the strongest fortress in Wales, but it was never finished. The inner towers never reached their full height and the castle saw little real fighting. Welsh forces under Glyndŵr held it briefly from 1403 before royal troops recovered it in 1405. Its reputation rests on design, not on any siege withstood.

Set on a rocky promontory almost wholly encircled by the tidal Pembroke River, with the great natural Wogan cavern hollowed beneath it, Pembroke is walled by water on three sides. Its huge round keep, four storeys under a stone dome, among the finest in Britain, anchored a curtain the medieval Welsh never breached.

Its hardest test came in the Second Civil War. From 31 May to 11 July 1648 Cromwell besieged it in person; his guns could not breach the walls and an assault on 4 June was thrown back. The castle fell only when his men located and cut the buried water conduit, forcing surrender by thirst, after which he had it slighted.

The oldest surviving stone castle in Britain, begun in 1067 on a cliff above the River Wye, with a Great Tower raised in stone from the outset when most castles were still earth and timber. The sheer limestone drop to the river guarded one whole flank while a line of baileys and gatehouses climbed the narrow ridge. Held for the King in the Civil War, it was besieged and taken twice, in October 1645, and again in May 1648, when the Royalist commander Sir Nicholas Kemeys refused to surrender and was killed as Parliamentarian guns broke into the keep.

Perched on a steep hilltop inside its own walled town, Denbigh was begun after 1282 by Henry de Lacy and fronted by a triple-towered great gatehouse, three octagonal towers massed over one guarded entrance, which John Goodall judged the most architecturally sophisticated gatehouse of the thirteenth century. Its record is mixed: the half-built castle was overrun in the Welsh revolt of 1294, and though it later resisted Glyndŵr, its severest trial was the Civil War, when a Royalist garrison withstood a six-month Parliamentarian siege before surrendering on terms on 26 October 1646, among the last mainland fortresses in Britain to fall.

A compact concentric fortress on a ridge above the Gwendraeth estuary: an inner square of four round towers set within a curtain wall, fronted by a formidable late-14th-century twin-towered gatehouse and backed by the river. The ground below saw the Welsh princess Gwenllian killed in battle in 1136. The defences held when it counted, during Glyndŵr's rising the town of Kidwelly was stormed in 1403 with loss of life, but the castle itself withstood the siege through to winter and was never taken.

Edward I's first concentric castle, begun in 1277 to James of St George's design: a diamond-plan inner ward with twin-towered gatehouses inside a lower outer wall and a dry moat. Its cleverest defence was logistical, Edward had hundreds of labourers canalise the River Clwyd over three years to bring a tidal dock right to the walls, so a sea-supplied garrison could never be starved out. Little troubled in the Middle Ages, it was held for the King in the Civil War and surrendered to Thomas Mytton in July 1646, after which Parliament slighted it, lowering the outer walls and breaching the inner.

The last great castle built in Wales, a mid-15th-century fortress-palace whose defences centred on the hexagonal Great Tower, the 'Yellow Tower of Gwent', a moated keep standing apart behind its own drawbridge, designed for the age of gunpowder. Later and less austere than the Edwardian giants, it nonetheless fought the hardest fight of any: in 1646 it endured the last major siege of the First Civil War, roughly 800 defenders under the Marquess of Worcester holding against some 3,500 Parliamentarians for about thirteen weeks before surrendering on 19 August 1646, the last significant Royalist stronghold to give in. Parliament then slighted the Great Tower, undermining it to the ruin seen today.