Roman Period

segontium (2) DSCF57494th century AD Greek Mosaic, British Museum.

Roman Period 60 A.D. – 411 A.D.


In A.D. 43, Roman Emperor Claudius began the military conquest of Britain and within 17 years in A.D. 61, Gaius Suetonius Paulinus defeated the Druids on Mona (Anglesey). The Romans believed that the Druids posed a threat to their rule by influencing the native tribes of Britain, by advising tribal chieftains who were putting up a resistance, and who encouraged their warriors to fight to death. The aim was to destroy the Druid order and the druidical centre on Anglesey.

Following the victory against the Druids, Gaius Suetonius Paulinus’ troops destroyed the sacred groves of the people. This was a very short-lived invasion, as Gaius Suetonius Paulinus withdrew his troops and marched them back south to defeat the revolt of Boudicca and the Iceni troops.

In A.D 78 – 79, Roman Governor, Julius Agricola continued the conquest of Mona, attacking the Decangli in Mona and gaining full control of the area. The remaining local tribes and communities apparently capitulated and settled under Roman administration. 

Roman Forts & Camps

segontium 3rd century

Some communities settled outside Roman forts in attached villages called a Vicus and may have been of a higher status than any other nearby settlements. Under these circumstances, they would have been subjected to Roman law and free to trade. Civilians were essential for use as a local workforce to build roads and to quarry stones.

Few hill tribes continued to trade and remained in smaller groups creating a Romano-British culture, living in smaller enclosed settlements. Farming would be an important contribution to the continuation of the Roman administration in North Wales. Although the Romans controlled the region, there was continuous guerrilla warfare in some highland areas.  

Segontium in Caernarfon was an auxiliary Roman fort established in 77-78 A.D by Julius Agricola originally built to command the Menai Straits to enable the capture of the island of Mona. It takes its name from the nearby River Seiont and possibly the Segontiaci, a British tribe mentioned by Julius Caesar.  It was the main Roman fort in the north of Roman Wales that lasted for around 330 years and was designed to hold about a thousand auxiliary infantry. It is approximate 150ft 45m above sea level on a natural plateau and commands an all-round view of the mountains, Menai Straits and Anglesey. It is of the usual playing card shape, in size 5.6 acres, 2.27 hectares with w shaped defence ditches and four gateways. It was garrisoned by cohorts of auxiliary and part mounted (Alae) troops. It was modified through to the late fourth century.

Below is a list of all the known Roman Forts & Camps in the area

I have included an O/S number on all historical sites to enable everyone to locate using an O/S map.


segontium DSCF4681

Segontium – main Roman fort of North Wales – Caernarfon SH485623

Bryn Glas – Roman signal station (rectangular enclosure) – Caernarfon SH502634

Dinas y Prif – Roman enclosed camp (earthwork) – Llanwnda SH463578

Caerlan Tibot – a small-defended enclosure (possible signal station) – Bethel SH507648

Coed Ty Mawr – possible late Roman period / early Medieval enclosed motte (earthwork) – Llanddeiniolen SH556663

Ty Mawr enclosed motte site - Copy

Tyn Llan Uchaf (church) – Roman defended enclosure (probable) – Llanddeiniolen SH544658

Lon Isaf –Roman signal point – (A55 roundabout) Llys y Gwynt, Llandygai SH596695

Pen-y-Gwryd – marching camp – (nr) Pen y Pass SH660557

Caer Llugwy, Bryn y Gefeiliau – Roman auxiliary fort – Capel Curig SH745573

Pant Glas – Roman marching camp – Bryncir SH477471

Derwin Bach – Roman marching camp – Bryncir SH477453

Pen Llystyn – Roman military auxiliary fort (now quarry) – Bryncir SH480449

Canovium – Roman auxiliary fort, defensive settlement & possible dock – Caerhun SH776703

Tomen y Mur – 120 AD – Roman auxiliary fort & defensive settlement, and a later Norman Motte was built on the site of the old Roman Fort  – (nr) Trawsfynydd SH705386


 Caer Leb

Tai Cochion – Roman settlement – Trefarthen, Brynsiencyn SH480657

Porthamel – British/Romano enclosed settlement (possible Iron Age Druid training school) – Llanedwen SH508679

Caer Idris – Roman settlement (possible Iron Age fort) – Brynsiencyn SH494680

Caer Leb – Iron Age / Romano-British settlement (earthwork) – Brynsiencyn SH473674

Rhuddgaer – Romano-British defensive settlement – (nr) Dwyran SH445642

Caer Gybi – Roman fort – Holyhead SH247827

Caer Twr – Roman hillfort – Holyhead SH218829

Hendrefor – Romano-British enclosed settlement (earthwork) – Llansadwrn SH545765

Bryn Eryr – Iron Age / Romano-British settlement (earthwork) – Llansadwrn SH540757

Holyhead Roman FortHolyhead Roman Fort

Some areas may be on private land and permission to roam may be required.
 There are public footpaths leading to most places.
Safety and care must be taken at all times, as some areas are difficult to get to due to hills and slopes that may lead away from paths.