The site of an extensive Roman military settlement (NPRN 92319) centred on a fort has been suspected since the late seventeenth century when Edward Lhuyd recorded coins, bricks and pottery at a location known as 'Cae'r Castell' to the east of Llanio-isaf Farm. Excavations were undertaken in the nineteenth and twentieth centuries, and features were also noted on aerial photographs in the dry summers of 1975 and 1976. Few traces remain on the ground, but a slight hollow marks the position of the headquarters building courtyard.

The fort occupied a low hillock in an area of broken, intermittently marshy ground on the edge of the Teifi floodplain. It was a near square enclosure with rounded corners, about 130m across and faced south-east towards the river crossing. Such a fort would have held a garison of at least 500 soldiers and the surrounding vicus settlement would have had a population of at least twice as many. It was established around AD 73 -77 and appears, on the basis of pottery finds, to have been abandoned around AD 120 - 130 or possibly earlier. Five inscribed stones have been discovered, two of which attest the presence of the Cohors II Astrium unit.

Sources: Willis Bund in Archaeologia Cambrensis 5th series 5 (1888), 279-319
St Joseph in the Journal of Roman Studies 51 (1961), 119-135
Jarrett in Archaeology in Wales 1 (1961), 6-7
Richmond and others in the Journal of Roman Studies 52 (1962), 160-190
Jarrett 'The Roman Frontier in Wales' 2nd edition (1969), 97-8
Davies in Archaeology in Wales 9 (1969), 17; 12 (1972), 23; 13 (1973), 38-9
in the 'Cardigan County History I (1994), 302-6
Hopewell 'Roman Fort Environs: Trawscoed & Llanio' GAT report No.623 (2006)

John Wiles, RCAHMW, 26 February 2008