Many Roman names were derived from ancient British or Brythonic. The Brythonic name Isca means "water" and refers to the River Usk. The suffix Augusta appears in the 7th century Ravenna Cosmography and was an honourific title taken from the legion stationed there. The later name, Caerleon, is derived from the Welsh for "fortress of the legion". Thi sphoto is taken looking into the arena of the amphitheatre. The legionary fortress lies behind the photographer.

Because of its rounded form, the unexcavated amphitheatre was known to locals as 'King Arthur's Round Table'. During excavations it was his revealed, among other things, that the amphitheatre had been built around AD 90, but had twice been partially reconstructed, once in the early part of the 2nd century, and again about a hundred years later. The arena is typically oval in shape, with eight entrances, and the stadium is thought to have had a capacity of around six thousand spectators.

This amphitheatre is the only fully excavated one in Britain. It was built around AD90 and its siting shows that the surrounding area must have been pacified. This room in the arena has the remains of a brick niche inserted in its rear wall - possibly a shrine to Nemesis (goddess of fate and divine vengeance).

The later history of the fortress was one of gradual decline, with detachments of the legion being withdrawn for deployment elsewhere. At the end of the third century much of the base was dismantled and the materials possibly reused in defences along the south coast. The area enclosed was some 50 acres. Outside the walls was a parade ground, the amphitheatre and an extensive civil settlement with shops and taverns ready to take the money off the troops.

The early fortress defences were of earth - an outer ditch and a rampart of turf and clay topped by a timber palisade. By the early second century these had been strengthened and a stone wall, with interval turrets and gateways, was built fronting the rampart.

The arena is hollowed out of the ground and was originally surfaced with sand. Earth banking, retained by buttressed stone walls, supported the lower tiers of wooden seats and massive timber superstructure carried the seating above.