About Caer Gybi
Caer Gybi in Holyhead contains the remains of a small Roman fortlet and naval base.
It is thought that Caer Gybi was constructed to defend against pirates who were operating in the area and this smaller fortlet was probably an outpost of the larger Roman fort at Segontium. It is believed that the Roman watchtower, which stood on the nearby Holyhead Mountain, served as the lookout post for Caer Gybi.
Although the construction date of Caer Gybi is unknown, it is believed that it was built in the late 3rd or early fourth century AD. The structure was made up of three defensive walls with circular watch towers at each corner. The fourth side of the fortlet fronted the sea and may have been a dock for the Roman warships which would have patrolled the area.
The Romans abandoned the region in the late fourth century AD and, by the 6th century AD, the site had been given to Saint Cybi who founded a monastery within the walls. The medieval Church of St Cybi still stands there today.
The architecture of Caer Gybi reflects other Roman defences of the time, many of which formed the "Saxon Shore" forts, and can still be seen in places such as Portchester Castle and Pevensey Castle. The construction even mirrors Roman sites further afield, such as the well-preserved Lugo Roman Walls in northern Spain.
Today, visitors to Caer Gybi can still view much of the original Roman defences, with walls standing up to 4m in places and at least one original corner tower.
Based on Wikipedia content that has been reviewed, edited and republished.