|Founded||77 or 78 AD|
|Abandoned||4th century AD|
|Place in the Roman world|
|— Stone structure —|
|Built||2nd century AD|
|— Wood and earth structure —|
|Built||1st century AD|
|Media related to Segontium at Wikimedia Commons|
Segontium is a Roman fort located on the outskirts of Caernarfon in Gwynedd, North Wales. The fort, which survived until the end of the Roman occupation of Britain, was garrisoned by Roman auxiliaries from present-day Belgium and Germany. It was the most important military base and administrative centre in this part of Britain.
Although the Roman occupation of Britain ended around 400AD, the legacy of the Segontium survived. The medieval name of the town Caernarfon is derived from "Caer yn ar-Fon" which means "Fort in (the land) opposite Mon".
Segontium was founded by Agricola in 77 or 78 AD after he had conquered the Ordovices in North Wales. It was the main Roman fort in the north of Roman Wales and was designed to hold about a thousand auxiliary infantry. It was connected by a Roman road to the Roman legionary base at Chester, Deva Victrix. Unlike the medieval Caernarfon Castle that was built alongside the Seiont estuary more than a thousand years later, Segontium was sited on higher ground to the east giving a good view of the Menai Straits.
The original timber defences were rebuilt in stone in the first half of the 2nd century AD. In the same period, a large courtyard house (with its own small bathhouse) was built within the fort. The high-status building may have been the residence of an important official who was possibly in charge of regional mineral extraction. Archaeological research shows that by AD120 there had been a reduction in the military numbers at the fort.
An inscription on an aqueduct from the time of the Emperor Septimius Severus indicates that by the 3rd century, Segontium was garrisoned by 500-men from the Cohors I Sunicorum, which would have originally been levied among the Sunici of Gallia Belgica.
The size of the fort continued to reduce through the 3rd and 4th centuries. At this time Segontium's main role was the defence of the north Wales coast against Irish raiders and pirates. Coins found at Segontium show the fort was still occupied until AD394.
Although the A4085 to Beddgelert cuts through the site, most of the fort's buildings are preserved. Guidebooks can be bought from other Cadw sites, including Caernarfon Castle. The remains of a civilian settlement together with a Roman temple of Mithras, the Caernarfon Mithraeum and a cemetery have been also identified around the fort.
Mythology and fiction
Segontium is referenced in the prose of the Mabinogion, a collection of early medieval Welsh poetry first collated in the 1350s. In Breuddwyd Macsen Wledig ("The dream of Macsen Wledig") - one of the Four Independent Tales - Macsen (who is identified with the Roman usurper, Magnus Maximus) dreams of a beautiful woman who turns out to be at "the fort at the mouth of the Seiont".
- Caer Gybi at Holyhead, was established in the 4th century to support Segontium against Irish raiders.
- Frances Lynch (1995) A guide to ancient and historic Wales: Gwynedd (HMSO)
- R.E. Mortimer Wheeler (1924) Segontium and the Roman occupation of Wales (Honourable Society of Cymmrodorion)