Arnulf of Montgomery built the first castle in 1093 on a promontory during the Norman invasion of Wales, though the text also says Roger of Montgomery founded it in 1073. Richard I arranged William Marshal's marriage to Isabel de Clare in 1189, and Marshal rebuilt the castle in stone and added the great keep. The infobox gives 1189 to 1218. The article calls it a Norman-style enclosure castle.
The keep is round with four stories linked by a spiral stair. It is 75 feet (23 m) high, with walls up to 20 feet (6 m) thick at the base. Wogan Cavern, a limestone cave beneath the castle, is reached by a 55-step spiral stair built in the 13th century. Margaret Beaufort gave birth to the future Henry VII here in 1457.
Oliver Cromwell took the castle after a seven-week siege in 1648 and ordered it destroyed. Major-General Sir Ivor Philipps began restoration in 1928. It is open to the public.

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