Dryslwyn Castle strategically crowns a hill that overlooks the Tywi valley. Originally the site of an early Celtic hill-fort, by the end of the 13th century Dryslwyn had become one of the largest Welsh castles in south Wales, the result of an expansion project undertaken by Rhys ap Maredudd. In 1287, Rhys became involved in a dispute with Robert de Tibetot the new Justiciar of west Wales and attacked the castles of Dinefwr, Carreg Cennen and Llandovery slaughtering their garrisons. King Edward I recaptured the castle after a three-week siege and Rhys was eventually caught and executed in April 1292 for treason. After the Owain Glyn Dwr revolt of 1403, the castle was deliberately dismantled to prevent future use by rebels.