Caer Gybi a small Roman fortlet located at the centre of Holyhead within the county of Anglesey, which was once in the Roman province of Britannia. Caer Gybi a small Roman fortlet located at the centre of Holyhead within the county of Anglesey, which was once in the Roman province of Britannia. The three-walled fort, with it`s fourth side fronting the sea is probably the site of a quay, thought to be part of a late 4th century build, associa more >> <<less