The Roman fort on the ridge above Pen-llwyn overlooked the Roman road where it crossed the River Rheidol. There are no surviving earthworks and it was first recognised from the air as a series of cropmarks. Small scale trenching confimed its identification as a Roman fort and geophysical survey has added much detail to the plan. It appears to have been established in the Flavian period and was occupied until at least AD 125 and possibly AD 140.

The fort covers approximatley 2.7ha and is one of the largest in West Wales - its size probably more the result of topography than importance. The triple ditch defences, with entrances in each side, measure 185m north-east to south-west by 140m, and have distinctive rounded corners. There was also an outer ditched circuit some 25-35m beyond the triple ditches on the north-west and south-east sides and running down to the river terrace some 250m distant on the south-west side. The way the fort has been fitted into the site's natural topography is interesting. The highest part is the rear, north-east division and the headquarters building occupied a sheltered hollow at the centre of the fort. The ramparts crown steep slopes on the north-east and south-west sides.

Sources: St Joseph in the Journal of Roman Studies 67 (1977), 152-4
Davies in the Bulletin of the Board of Celtic Studies 33 (1986), 414-28
in the Cardigan County History I (1994), 298-9
Cambria Archaeology website (geophysical survey)

John Wiles, RCAHMW, 27 February 2008.