- Celtic: caer, fortress; Latin: legionum, of the legions: from its being the headquarters for over 200 years of the Roman Second Legion
Town in Monmouthshire on Usk River, associated with the legends of King Arthur. It was the seat of a bishopric, afterwards transferred to Saint Davids. In 973 King Edgar was rowed by eight kings at Caerleon. The remains of a Roman amphitheater are to be found here.