Caerleon is a small Welsh town beside the River Usk, a few miles north of Newport. The name "Caerleon" in Welsh means "City or Fort of the Legion." Legend says that after the Romans left Britain, Arthur set up court at Caerleon. The city of Caerleon is linked with Arthur in many texts, including Geoffrey of Monmouth's History of the Kings of Britain, and the Welsh Mabinogion.
The sheer number of mentions of Caerleon (The City of the Legion) attests to its claim to have a connection to Arthur. It has been contended that Geoffrey chose Caerleon as Camelot because it is near his home town of Monmouth. The town of Caerleon is mentioned though as Arthur's palace in the Welsh Triads and the Mabinogion, which were written before Geoffrey. Another earlier reference to Caerleon is made by Nennius--the ninth battle of Arthur is said to have been at the City of the Legion.
The town of Caerleon is built on an old Roman legionary base. Many of these Roman structures remain today. Even more of these structures would have existed and would been in better condition in Arthur's day, and this would have made this a desirable Camelot. The Caerleon amphitheater just outside the partially preserved city walls is smaller in scale than the Colosseum but is still distinctly Roman. The foundations of the Roman barracks and parade grounds are nearby. Inside the town, there is a Caerleon museum that houses remnants from the Roman reign.
When this proud company of kings, bishops, and princes was gathered together
to observe Arthur's feast, the whole city was moved. The king's servants toiled
diligently making ready for so great a concourse of guests. Soldiers ran to
and fro, busily seeking hostels for this fair assemblage. Houses were swept
and garnished, and furnished with hangings of rich arras...The city was full
of stir and tumult...Caerleon seemed rather a fair than a city,
at Arthur's feast.
-Wace, Roman de Brut, page 66.
King Arthur was at Caerlleon upon Uske; and one day he sat
in his chamber; and with him were Owain the son of Urien,
and Kynon son of Clydno, and Kai the son of Kyner; and Gwenhwyvar and her handmaidens at needlework by the window
and if it should be said that there was a porter at Arthur's palace, there was none.
-The Lady of the Fountain in Guest, page 151.
Situated as it [the City of the Legions] is in Glamorganshire,
on the River Usk, not far from the Severn sea, in a most
pleasant position, and being richer in material wealth than other townships, this city was eminently suitable for such a ceremony [as the celebration of Whitsun].
-The History of the Kings of Britain
Local legend at Caerleon tells of an undergound chamber in the woods where a thousand of Arthur's soldiers lie sleeping, awaiting the day when Wales will need them.
Caerleon certainly has a large number of refernces to in in King Arthur literature.
Arthurian Sites in Wales