Cefnllys Castle.
Cefnllys Castle was a medieval spur castle sited on a ridge – possibly an earlier Iron Age hillfort – above the River Ithon in Radnorshire, Wales. The first masonry castle at the site was constructed around 1242 to control several routes through the Welsh Marches. Cefnllys became a source of friction between Llywelyn ap Gruffudd and Roger Mortimer in the prelude to Edward I's conquest of Wales. The castle was captured and razed in 1262 by Llywelyn, during a war with Henry III of England, and Cefnllys featured prominently in the ensuing peace treaty. The construction of a new castle was a contributing factor to Llywelyn's refusal to swear fealty to Edward I in 1275, leading to war in 1276. The castle may have been sacked during the revolts of Madog ap Llywelyn (1294–1295) and Owain Glyndŵr (1400–1415), but it remained occupied until at least the mid-15th century. Both castles are now entirely ruinous and only traces remain.
