The Cistercian abbey of Cwm-hir is of great historical significance. Its early history is somewhat obscure but the permanent foundation dates to 1176. It was twice attacked during the late twelfth century by Hugh de Mortimer and eventually given a Norman charter. From 1197 onwards, the earlier wooden building began to be replaced by a more permanent stone structure and, although it was never fully completed, the abbey was, at this time, of a size that was only surpassed by those at York Durham and Winchester .There is a also long-standing tradition, based on the evidence of one chronicle, that the body of Llywelyn ap Gruffudd was buried at Abbey Cwmhir after his death at Cilmeri, near Builth Wells, in 1282.