Iron Age – Defensive Hillforts

The age of the Iron Age Hillforts in Wales started sometime around 700BC until around 60AD when the Roman Empire had successfully subdued the local Celtic tribes and chieftains.

Although hillforts are known during the Bronze Age, the golden Age of hilltop fortification took place during the Iron Age. However, some hillforts were still in use during the Roman period. These are known as Romano-British defensive enclosed settlements and it is apparent that most communities quickly settled down under Roman rule.

Hillforts were constructed for defensive purposes. However, there is no clear evidence as to why they were constructed as most were without any source of water and unlikely to have been used as permanent settlements or as long-standing locations for tribal warfare. Although hillforts were designed to withstand a small-scale attack, it is quite probable that they were constructed as a deterrent.

Some historians believe that hillforts were constructed by the Celtic migrants as they settled on territories controlled by the native Britons, or even by the natives to deter the migrating Celts. It has also been suggested that hillforts were a place of tribal gathering, a meeting point for local tribes and a chance for them to show off their power, i.e. the larger the defence the more the power and less likely to be attacked.

Below is a list of all the known Iron Age Hillforts in the area

There are many different kind of hillforts scattered throughout Gwynedd, the most spectacular being Tre’r Ceiri hillfort on Lleyn Peninsula that includes 150 hut circles and the impressive Dinas Dinorwic defensive hillfort, former stronghold of the Ordovices.

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



Maes y Gaer – Iron Age hillfort – Abergwyngregyn SH663725

Pen y Gaer – Iron Age hillfort – Bethesda SH628672

Ty’n Ffridd – Iron Age defended settlement – Rachub SH62826790

Pen Dinas – Iron Age defended hillfort – Tregarth SH610680

Garth (Pier) Camp – Iron Age hillfort – multi period use (earthwork) – Bangor SH580728

Dinas Camp – small Iron Age promontory fort (also probable Roman) – Felinheli SH518672

Crug Camp –  Iron Age / Romano-British – multi period defensive earthwork – Crug House, Bethel SH639653

Dinas Dinorwig – Iron Age hillfort – Llanddeiniolen SH549653

Dinas Dinorwic hillfort

Caer Glascoed – defensive Iron Age / Romano-British enclosure – Llanddeiniolen SH548643

Dinas Mawr – defensive enclosure & nearby hut settlements – Penisarwaun SH553636

Caer Carreg y Fran – early Iron Age hillfort – Cwm-y-Glo SH547627

Dinas Ty Du – Iron Age fortified hillfort – Llanberis SH565609

Caer Carreg y Fran

Caer Ty Du

Dinas Dinoethwy – defensive Iron Age hillfort (probable) – Bontnewydd SH487591

Y Gadlys – Iron Age & later medieval defensive fort – Llanwnda SH480579

Bedd Gwernan –Iron Age defended enclosure (probable) – Llandwrog SH45564

Dinas Dinlle – Iron Age hillfort – Llandwrog SH436564

Plas Newydd – Iron Age defensive fort (un-investigated)Glynllifon, Pontllyfni SH450541

Bryngwydion – Iron Age defended enclosure (probable / earthwork) Pontllyfni SH442535

Foel Hillfort – Iron Age defended enclosure camp – Clynnog SH450507

Craig y Dinas – Iron Age defensive enclosure – Llanllyfni SH448520

Caer Engan – Iron Age (Celtic) hillfort – Llanllyfni SH477526

Gelli Ffrydiau – Iron Age defensive hilltop enclosure – Nantlle SH525535

Castell Caerau – Iron Age hillfort – Dolbenmaen SH509439

Craig y Tyddyn – defensive enclosure – Dolbenmaen SH505427

Dinas Emrys – Iron Age / Romano-British / early medieval (rems) Beddgelert SH607491

Dinas – Iron Age defended hillfort – Beddgelert SH591488

Pen y Gaer – defensive hillfort – (nr Aberglaslyn Pass) Nantmor SH586457 


Pen y Gaer, Caerhun

Dinas (Nant y Coed) – Iron Age hillfort – Llanfairfechan SH700738

Braich y Dinas – Bronze Age / Iron Age / Roman (destroyed by quarry)Penmaenmawr SH693755

Dinas Alltwen – defensive hillfort – Dwygyfylchi SH744772

Castell Caer Seion – Iron Age hillfort (60 hut circles)Mynydd y Dref, Conwy SH758777

Pen y Dinas – large Iron Age hillfort – Great Orme, Llandudno SH779829

Cerrig y Ddinas – Iron Age hillfort – Henryd, Conwy SH754739

Caer Bach – early Iron Age hillfort – Rowen SH743730

Pen y Gaer – Iron Age hillfort (20 hut circles) – Caerhun SH750692


Tre'r Ceiri - the impressive Iron Age hillfort on the Lleyn Peninsula

Tre’r Ceiri – Iron Age hillfort / Romano-British (150 huts circles) – Llanaelhaearn SH373447

Pen y Gaer – Iron Age hillfort – Llanaelhaearn SH428455

Carn Pentyrch – Iron Age defensive hillfort – Llangybi, Four Crosses SH424417

Garn Boduan – late Iron Age hillfort (170 hut circles) – Nefyn SH311391

Dinllaen – promontory fort (ruined by golf course) – Morfa Nefyn SH275418 

Garn Fadrun – Iron Age fort  / Romano-British / early medieval castle (rems) – Tudweiliog SH280350

Garn Saethon – defensive enclosure – (nr Garn Fadrun) Llanfihangel SH298338

Pen y Gaer (Llanbedrog) – Iron Age promontory hillfort – Llanbedrog SH323314

Pen y Gaer (Abersoch) – Iron Age defensive hillfort – Abersoch SH298282

Castellmarch / Castell Abersoch – Iron Age defended enclosure – Abersoch SH313285

Castell – Iron Age hillfort – Llanengan SH294267

Pared Mawr /Porth Ceiriad – Iron Age promontory fort – Llanengan SH303246

Castell Caeron – Iron Age hillfort – Botwnnog SH232303

Rhiw – Iron Age defensive enclosure – Rhiw SH230283

Creigiau Gwineu – defensive hillfort – Mynydd y Graig, Rhiw SH228274

Castell Odo – Iron Age Celtic hillfort – Aberdaron SH188284


Din Lligwy Ancient Vilage Din Lligwy, Ancient Village

Din Sylwy / Bwrdd Arthur – Iron Age hillfort / Romano-British – Llanddona SH586814

Dinas Cadnant – Iron Age defensive enclosure (earthwork)– Menai Bridge SH551733

Castell Bryn-Gwyn – late Neolithic religious sanctuary to Roman period fortified settlement (earthwork) – Brynsiencyn SH466671

Moel-y-Don – Iron Age defensive promontory fort to early Medieval – (nr) Brynsiencyn  SH516678

Trwyn-y-Parc – Iron Age promontory fort (possible Roman) – Bodorgan SH370650

Y Werthyr – Iron Age hillfort (prehistoric) – Bryngwran SH374782

Dinas Porth Ruffydd – Iron Age defensive promontory fort – Trearddur SH225795

Dinas Gynfor – Iron Age hillfort – Llanbadrig SH390951

Din Lligwy – Iron Age & Romano-British defensive settlement – Moelfre SH495862

Parciau Hillfort – Iron Age / Romano-British defensive settlement – Benllech SH594847

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.