Caernarvon Castle. Caernarfon Castle, often anglicised as Carnarvon Castle or Caernarvon Castle, is a medieval fortress in Caernarfon, Gwynedd, north-west Wales cared for by Cadw, the Welsh Government's historic environment service. It was a motte-and-bailey castle from the late 11th century until 1283 when King Edward I of England began to replace it with the current stone structure. The Edwardian town and castle acted as the administrative centre of north Wales, and as a result the defences were built on a grand scale. There was a deliberate link with Caernarfon's Roman past, and the Roman fort of Segontium is nearby. While the castle was under construction, town walls were built around Caernarfon. The work cost between E20,000 and E25,000 from the start until the work ended in 1330. Although the castle appears mostly complete from the outside, the interior buildings no longer survive and many of the building plans were never finished. The town and castle were sacked in 1294 when Madog ap Llywelyn led a rebellion against the English. Caernarfon was recaptured the following year. During the Glyndwr Rising of 1400-1415, the castle was besieged. When the Tudor dynasty ascended to the English throne in 1485, tensions between the Welsh and English began to diminish and castles were considered less important. As a result, Caernarfon Castle was allowed to fall into a state of disrepair. Despite its dilapidated condition, during the English Civil War Caernarfon Castle was held by Royalists, and was besieged three times by Parliamentarian forces. This was the last time the castle was used in war. The castle was neglected until the 19th century when the state funded repairs. The castle was used for the investiture of the Prince of Wales in 1911 and again in 1969. It is part of the World Heritage Site Castles and Town Walls of King Edward in Gwynedd. The first fortifications at Caernarfon were built by the Romans. Their fort, which they named Segontium, is on the outskirts of the modern town. The fort sat near the bank of the River Seiont; the fort was probably built here due to the sheltered position and because it could be resupplied via the river Seiont. Caernarfon derives its name from the Roman fortifications. In Welsh, the place was called y gaer yn Arfon, the Welsh name for Anglesey. Little is known about the fate of Segontium and its associated civilian settlement after the Romans departed from Britain in the early 5th century. Following the Norman Conquest of England, William the Conqueror turned his attention to Wales. According to the Domesday Survey of 1086, the Norman Robert of Rhuddlan was nominally in command of the whole of northern Wales. He was killed by the Welsh in 1088. His cousin Hugh d'Avranches, Earl of Chester, reasserted Norman control of north Wales by building three castles: one at an unknown location somewhere in Meirionnydd, one at Aberlleiniog on Anglesey, and another at Caernarfon. This early castle was built on a peninsula, bounded by the River Seiont and the Menai Strait; it would have been a motte and bailey, defended by a timber palisade and earthworks. The motte, or mound, was integrated into the later Edwardian castle, but the location of the original bailey is uncertain, although it may have been to the north-east of the motte. Excavations on top of the motte in 1969 revealed no traces of medieval occupation, suggesting any evidence had been removed. It is likely that the motte was surmounted by a wooden tower known as a keep. The Welsh recaptured Gwynedd in 1115, and Caernarfon Castle came into the possession of the Welsh princes. From contemporary documents written at the castle, it is known that Llywelyn the Great and later Llywelyn ap Gruffudd occasionally stayed at Caernarfon. War broke out again between England and Wales on 22 March 1282. The Welsh leader, Llywelyn ap Gruffudd, died later that year on 11 December. His brother Dafydd ap Gruffydd continued to fight against the English, but in 1283 Edward I was victorious. Edward marched through northern Wales, capturing castles such as that at Dolwyddelan, and establishing his own at Conwy. War finally drew to a close in May 1283 when Dolbadarn Castle, Dafydd ap Gruffudd's last castle, was captured. Shortly afterwards, Edward began building castles at Harlech and Caernarfon. The castles of Caernarfon, Conwy and Harlech were the most impressive of their time in Wales, and their construction, along with other Edwardian castles in the country, helped establish English rule.