This tremendous stronghold was in Welsh Yr Gaer in Arfon, “The Fortress on the Shore,” built on the Menai Strait so that if besieged it could be supplied from the water. The Welsh lords of Gwynedd had a fortress on the site, and the Romans had built a fort centuries earlier nearby, at what they called Segontium, fragments of which have survived. The Roman connection may well have Influenced Edward I’s decision to build the present castle as a statement of English domination, after the last independent Welsh prince, Llewellyn the Last, was killed in battle in 1282.

The castle was designed by Edward’s military architect, James of St. George. Unlike such castles as Harlech and Beaumaris, it was not simply a military stronghold—although its walls were still 20 feet (61 m) thick at the base. Caernarfon Castle was to be the capital and epicenter of English power in Wales. The Welsh settlement on the site was destroyed and a new
town was built at the same time as the castle, enjoying its protection as well as its own protective wall.

Edward’s son, the future Edward II, was born in Caernarfon (or, in English, Caernarvon) in 1284, apparently in a little room in the Eagle Tower, and his father took the opportunity to show him off triumphantly to the people as their new Prince of Wales. He is said to have announced that he was giving the Welsh a prince born in Wales, who could not speaka word of English.

In 1294 the castle was taken by the Welsh, but was recovered by Edward I. Building work on it did not end until around 1330. Owen Glendower failed to seize it in the 1400s. During the Civil War in the seventeenth century, It was held by Royalists and Roundheads alternately, and it was Parliament that had it reduced to a shell. Prince Charles, oddly garbed, was invested as Prince ofWales at Caernarfon in 1969.