Caerleon is the site of a Roman fortress named Isca Augusta ("River of the Augustan Legion") or Isca Silurum ("River of the Silures"). It became the headquarters of the Legion Secunda Augusta (Second Augustan Legion) in roughly AD 75, when Sextus Julius Frontinus, governor of Britain from 74 - 78, began conquering Wales. It was originally built with a timber palisade which was later replaced with stone and had the usual buildings for a fortress: headquarters, legate's residence, tribunes' houses, hospital, bath house, workshops, barracks, granaries, and an amphitheater. By the 120s, Caerleon had declined in importance as detachments or vexillations of the legion were needed elsewhere. Each cohort still maintained a presence at Caerleon, however, and when Septimius Severus became Emperor in 193, he had the fortress refurbished and the legion returned after heavy losses on the continent. Isca Augusta underwent further restoration under Severus' son, Caracalla. The legion was later called away to fight for one of the emperors in the late 200s, although a "caretaker" squad was left to keep the fortress in shape. The fortress was abandoned in the 290s by either Carausius or Allectus, after which the people of the surrounding area took it over.
The most convincing evidence for Camelot at Caerleon is the amphitheater. It was known to the locals as King Arthur's Round Table in the Middle Ages, and was excavated in 1926. It is oval, has eight entrances, and has seats for around six thousand spectators. However, there is no other evidence for Arthur at Caerleon. As well, there are no signs of rebuilding in the 400s or 500s, although the restorations of Severus and Caracalla are evident. It should be noted that it is only a short distance from Caerwent - roughly half an hour to one hour on horseback. It is possible that Caerleon was used to marshal Arthur's troops, hence the local name of the "Round Table" given to the amphitheater and Caerwent was the actual capital of Arthur's kingdom.
