This was much or even more the case with the castles of Cardigan, which, though usually small, and with two or three exceptions not individually of great importance, were very numerous, and collectively served sufficiently well for the ordinary defence of the territory. They were almost all founded by the De Clares and their followers early in the twelfth century. At the head of them and exceptionally strong stood Aberystwith near the north of the county, upon the shore of Cardigan Bay, and partly covered by the junction of the Ystwith with the Rheidol. Its position on the sea and in the rear of the strongest parts of South Wales made it particularly obnoxious to the Welsh; it was exposed to the full fury of the attacks from both North and South Wales, and strong as it was both by art and nature, was often taken and retaken, destroyed and rebuilt. Between it and the extreme limit of the county, the Dyfy, were the lesser castles of Geneur-glyn and Glan-Dyfi, and near it was Stradpythyll Castle, built by Ralph, steward to Earl Gilbert. It was besieged in 1122. Cardigan is traversed obliquely by the Teivi, and near the head of that stream was the great castle of Ystrad-Meyric founded by Gilbert de Clare, of which the ruins remain. Tregaron was lower down, as were a number of other strong places, such as Llanllwyni, Llanfihangel, Llandissul, Llangollen, of which it is difficult to say whether they were castles of the de Clare period or earlier residences. Blaen-porth-gwythian Castle was built by Earl Gilbert before 1112. At Newcastle was a strong castle also on the Teivi, and nearer to the mouth of the river, on the Cardigan bank, the castle of the town of Cardigan. Besides these there occur in local histories the names of Castell-Gwynionydd or Coedvon near Llampeter; Castell Abereinon; Humphrey’s Castle in Llandissil; Blaen Porth near Cardigan; Iscoed, where the mound seems to have had a keep in masonry; Llanven; Llampeter, where the mound remains but the masonry has been removed; Dinerth, the mound of which is called Danish, but where Roger de Clare founded a castle in 1135; Castel Rhos in Llanyrysted, built in 1158; Caerwedro, taken by the Welsh in 1135; and Llanyondri.