During the late 1270′s and early 1280′s, particularly after the death of Llywelyn ap Gruffydd, Edward I began construction of a string of castles in Wales that circled the country. The north, in Gwynedd, had always been a hotbed of Welsh resistance and resentment of English authority and it was there he built some of the most impressive of his monuments. http://www.castlewales.com/edward1.html
The three castles of north east Wales, from east to west, are Hawarden, Flint, and Rhuddlan.
Hawarden was built before the conquest of Wales, and was the first castle attacked by Dafydd ap Gruffydd in 1282 when he began the final war with England. Edward began Flint in 1277, bringing in up to 2300 English workers to build it. Llywelyn ap Gruffydd submitted to Edward I at the old timber Rhuddlan Castle, towards the end of 1277 after the construction at Flint was well underway. Immediately thereafter, Edward pulled down the old structure and began work on the present, massive, stone castle, built at the first usable ford of the Clwyd River, south of the sea.
Following along the north coast, come Conwy, Beaumaris, and Caernarfon, bringing the string of powerful castles across the coast of north Wales to six, within a stretch that was fewer than 60 miles as the crow flies. Source for the map: http://www.timeref.com/castedwd.htm
Conwy was begun in March of 1283, before the death of Dafydd ap Gruffydd and is located on the west bank of the Conwy river, which is of more than symbolic significance. It was the Conwy River that was the barrier between east and west Gwynedd, and the difficulty in forcing it that delaying Edward’s conquest of Wales. With a massive castle on the west bank of the river, he gained a permanent foothold in Snowdonia and the patrimony of the Princes of Gwynedd.
Beaumaris was built on Anglesey, near the ruins of Llanfaes Abbey (which the English destroyed), which had been patronized by the Welsh Princes. At one point, the sarcophogus of Joanna, Llywelyn Fawr’s wife, was used as a horse trough, but is now on display at the castle. The castle wasn’t built until 1295, as a result of the rebellion in late 1294 by Madog ap Llywelyn. The entire population of Llanfaes was moved in order to build it.
Edward built Caernarfon (or Caernarvon, the English spelling, since the Welsh town was destroyed to build it and English settlers brought in, much like at Rhuddlan and Conwy), beginning in May, 1283. It became his primary seat in Wales, and it was here that his son, Edward II was born–intentionally–to give credence to Edward I’s later naming of him the Prince of Wales.
The final two castles in Edward’s building program are Aberystwyth and Builth/Buellt. Edward began Aberystwyth on the west coast of Wales in 1277 as a concentric castle (near/on the foundations of much older castles), but conspirators of Dafydd ap Gruffydd attacked it on Palm Sunday, 1282, damaging it badly. Thus, it wasn’t until the Welsh defeat at the end of 1283 that construction began again, finishing in 1289. Today, it is one of the more crumbled of Edward’s castles, although not as damaged as Builth in Powys, of which only grassy mounds remain.
Like Aberystwyth, Edward began building Builth Castle in 1277, in response to the defeat of Llywelyn ap Gruffydd. It was near this castle, in fact, that Llywelyn was set upon and murdered in December of 1282.