The fort at Colwyn Castle is thought to represent a Roman auxillary camp established during the Roman thrust through mid-Wales to confine the northern edge of the Silurian territory in the pre-Flavian (pre AD 69) era. A pottery assemblage recovered during excavations demonstrated its continuation as a military site into the early second century.
It is a round angled, rectangular earthwork, 170m north-east to south-west by 160m, its north-east side overlain by earthworks of a medieval castle (Nprn92387). Excavations in 1975 and a watching brief on construction work in 1972 identified pits and possibly burnt timber buildings. No evidence of a vicus has been identified.