Caer Gybi in Holyhead contains the remains of a small Roman fortlet and naval base, whose atmospheric ruins can today be explored. Although the construction date of Caer Gybi is unknown, it is believed that it was built in the late 3rd or early 4th century. The structure was made up of three defensive walls with circular watch towers at each corner, while the fourth side fronted the sea and may have been a dock for the Roman warships that would have patrolled the area.
It is thought that Caer Gybi was constructed to defend against Irish sea raiders, and as a 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.
The Romans abandoned the region in the late 4th century, and by the 6th century 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.
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.
References:The Broch of Clickimin is a large and well preserved, though somewhat restored broch near Lerwick. Originally built on an island in Clickimin Loch (now increased in size by silting and drainage), it was approached by a stone causeway. The water-level in the loch was reduced in 1874, leaving the broch high and dry. The broch is situated within a walled enclosure and, unusually for brochs, features a large 'blockhouse' between the opening in the enclosure and the broch itself. Another unusual feature is a stone slab featuring sculptured footprints, located in the causeway which approached the site. Situated across the loch is the Clickimin Leisure Centre.