The Roman military settlement at Pen Llystyn lies on the Roman road between Caernarfon and Tomen y Mur at a strategically important position between the Lleyn Peninsula and the Snowdonia Mountains. It was the subject of extensive rescue excavations between 1954 and 1962 (Hogg 1959; 1969) when much of the internal arrangement of buildings was recorded prior tothe fort's almost complete removal by gravel extraction operations.

The settlement was centred on an auxiliary fort established in the late AD 70s that continued in use until about AD 90 when it appears to have been deliberately burnt down by its garrison and abandoned. A smaller fortlet was later established in the northern corner in the first quarter of the second century, but this was abandoned around 125 AD.

A rectangular enclosure revealed through geophysical survey on gently sloping ground north-west of the fort could be related to the settlement and a probable Roman temporary camp (NPRN 302405) has been identified on the far side of the Dwyfach river, north-west of the fort.

Sources: Griffiths in Archaeologia Cambrensis 108 (1959), 114-25
Hogg in the Transactions of the Caernarvonshire Historical Society 20 (1959), 1-5
in the Archaeological Journal 125 (1969 for 1968), 101-192
Jarrett in 'The Roman Frontier in Wales' 2nd edition (1969), 101-103
White in the Bulletin of the Board of Celtic Studies 28.2 (1979), 347-8
Hopewell in Britannia 36 (2005), 235-7

John Wiles, RCAHMW, 30 May 2007