Carleon-Upon-Usk

 http://www.kingarthursknights.com/structures/carleon.asp Gwent, Wales

According to Geoffrey of Monmouth's twelfth-century History of the Kings of Britain, this was Arthur's chief city. In a lengthy description, it is made to rival the later Camelot in its splendour. It contained two minster churches where choirs sang praises to God non-stop, and a college of 200 

The Round Table was once believed to have stood here.

scholars skilled in the arts of astrology and prediction. This is where Arthur was crowned and held his first court, presiding over a rich company including liveried knights and their ladies.The present site contains the ruins of a fine Roman amphitheatre and extensive buildings, including bath houses and barracks. Until recent times, the central mound of the amphitheatre was called 'The Round Table'. Geoffrey's account probably lies behind this identification, and it was almost certainly prompted by his own patriotism - Monmouth, where Geoffrey was born, lies only a little way to the north. The town's Roman name, City of Legions (Caer-Leon) led to its identification as the possible site of the ninth of the twelve great battles fought between Arthur and the Saxons.