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 – Rachub SH628672
  • Pendinas –Iron Age minor hillfort & nearby settlement – 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.