What was Dun Aengus? Ireland's Ancient West Maritime Hub

Table of Contents

There are few more exhilarating sites that standing on Ireland’s west coast and staring out across the seemingly endless ocean before you. The chill breeze, pungent smell of kelp, cawing of gulls, and sound of crashing waves. It’s a scene that has stood still for millennia; a frozen tableau that Ireland’s ancient forbears would have enjoyed as much as we today. And it’s the scene that greets you at one of Ireland’s most remarkable sites: the Dun Aengus Fort (Dún Aonghasa).

Dún Aonghasa is located on the Arran Islands off the West coast of Ireland near Galway on the island of Inishmore. The original hillfort was constructed around 1000BC and there’s evidence of habitation right through the Bronze Ages, Iron Age, and into the early Medieval period up to the 10^th century AD.

Historical Timeline of the Dun Aengus Fort

Period / year	Event
c. 1100 – 800 BC	First inner enclosure constructed; charred timbers & pottery give Late Bronze-Age horizon.
500 – 200 BC	Outer walls and chevaux-de-frise added; sling-stone dumps imply Iron-Age conflict.
AD 500 – 700	Re-occupation; hearths cut into earlier debris; glass beads & bone comb suggest high-status use.
1684	Roderick O’Flaherty’s Ogygia first antiquarian description; fort called “Dun Ængus”.
1880	State guardianship (Board of Works) begins; minor consolidation.
1992 – 1995	Claire Cotter leads Western Stone Forts Project excavations & conservation.
2005 – 2007	OPW installs cliff safety barrier, paths & visitor centre.
2023	Digital photogrammetry survey published (Heritage Ireland) – updated 3-D model online.

Mythical beginnings

Dún Aonghasa, meaning ‘Fort of Aonghas’, likely refers to King Aonghus mac Úmhór who ruled the ancient Fir Bolg peoples of Connacht. After the Fir Bolg were defeated by the invading Tuatha De Danann, legend states, King Aonghus built this fortress for his people as they settled of the coast of Connacht.¹

“The Fir Bolg fell in that battle all but a few, and they went out of Ireland in flight from the Tuatha De Danann, into Ara, and Ile, and Rachra and other islands besides….[F]rom them are named those territories…[including] the Fort of Oengus in Ara from Oengus.”²

While the myths tell us little about the actual composition or history of the hillfort, it does reinforce its significance. For the fort, like those other ancient sites of Tara, Rathcroghan or Emain Macha, was of sufficient political importance to be placed within the earliest mythological narratives of Ireland. To understand the wider context of these myths then requires turning to the archaeological evidence.

Landscape photograph of Dun Aengus on the Aran Islands, Ireland. Copyright: Lorenz

Archaeology of Dun Aengus: Formidable fortification

The hillfort would have required significant labour to build as “a costly signal of power of the local elite”.³ Consisting of three walled fortifications containing a mixture of domestic structures, the fort was one of the largest in Ireland. The outer, middle and inner walls form three semi-circular enclosures which terminate abruptly at the cliff-edge; a sheer 100m high drop today. Some have estimated – due to lower sea levels at the time of construction, that the cliffs may have once been an incredible 1000m high, though I personally find this unlikely for many ecological and geological reasons.

Besides its breathtaking location against the cliffs, the fort has a series of remarkable stonework defensive features. An array of stone slabs have been set in place around the middle enclosure, some as large as 2m tall. As a result, any approaching army would have been forced to break apart their shieldwall greatly undermining their defensive advance. The technical term for such a feature is a chevaux de frise, meaning Frisian horse, as such structures have historically been employed as anti-cavalry defences right up to the 19^th century (think of barbed wire barriers). To have gone to the effort of constructing such an impressive defensive feature suggests this was both a deeply contested territory and one worth protecting.

Comparison between Dun Aengus and other Hillforts

Fort	Secure date-range	Notable feature(s)
Dún Aengus	c. 1100 BC (LBA) → additions up to early medieval	Cliff-edge truncation, Western Stone Forts excavation (1992-95)
Staigue Fort	300 – 400 AD (radiocarbon charcoal)	Intact stairways; surrounding ditch absent
Grianán of Aileach	Built 6th–8th c.; rebuilt 1870s	Triple wall passages; royal inauguration site
Dún Dúchathair	Iron Age (c. 500–200 BC)	Interior terracing, twin gateways
Caherconnell	10th–12th c. (AMS dates)	Evidence for metal-working & cattle corrals

Photograph of the Chevaux de Frise at Dun Aonghasa or Dun Aengus — Chevaux de Frise at Dun Aonghasa
Copyright: Tuoermin

Ancient trade hub

It was strategically placed to control Atlantic maritime trade corridors, some consisting of long-distances far beyond the Irish shores as far afield as Northern Italy.⁴ Examples include “Beads made from Baltic amber” and a wide variety of exotic bronze objects.⁵ The hillfort’s location was strategically placed to “dominate seagoing traffic and serve as an economic hub for maritime exchange along the west coast”.⁶ In other words, it acted as an ancient Irish market-town. Travelling merchants would have been able to rest and recuperate at hostels and lodgings, trading their goods at local markets, before then moving on.

Notably, there were a range of moulds discovered on site alongside metalworking debris which indicate metalworking on the island itself on an industrial scale. Many of these objects were likely produced, not merely for the immediate locality, but as part of a thriving trade network with Europe. Indeed, the archaeological excavations at the site have identified an incredible array of over 2,900 artifacts.

Archaeological Finds at Dun Aengus

Find category	Quantity / items	Date attribution
Coarse-ware pottery sherds	176 stratified fragments	Late Bronze Age
Glass beads (blue & amber)	5 complete; 3 frags.	Early Iron Age
Bronze socketed spearhead tip	1 fragment	c. 800–600 BC
Bone points & needles	22	LBA–IA
Hammer-stones & pounders	47	Multi-phase
Charred barley & emmer grains	310 grains (multi contexts)	14C 920–810 BC
Sheep/goat, cattle, pig bone	4.8 kg assemblage	LBA core

Regional centre of power

Hillforts located on neighbouring islands show remarkable similarities but all on a much smaller scale. This has led archaeologists to suggest that Dún Aonghasa was likely a regional power centre over this network of small islands and nearby coastland.⁷ Interaction between regional chiefs would have been episodic, likely at important festivals and religious occasions. Evidence of feasting at the site indicates it had a “ritual significance”.⁸ For instance, pig bone found on site indicates it was imported (given the island hadn’t the tree coverage to support a pig population) and so was brought possibly by other elites “for communal feasting events”.⁹

Given its economic importance as a trade hub and industrial centre (at least in metalworking), alongside its strategic defensive importance at the boundaries between the Kingdoms of Connacht of Munster, it would have undoubtedly played a critical role in the politics of the wider region. Whatever chief ruled there would have profound implications on much further afield than the islands and coastland. And the remaining walls and scale of the site today only serves to reinforce this impression.

Dún Aengus Today

Since 1880 the Irish Government has taken over the management of the site and it is now open to the public to visit. Ferries run regularly to the island and there’s a variety of accommodation available to stay on site. For more visitor information see here.

Frequently Asked Questions: Dun Aengus

When was Dun Aengus built?

Radiocarbon and artefact evidence place initial construction in the Late Bronze Age (c.1100 BC), with Iron-Age and early-medieval modifications.

What is a chevaux-de-frise?

A dense band of tall, sharpened upright stones encircling the fort to slow attackers—unique among Irish ringforts.

How high is the cliff at Dun Aengus?

Approximately 100 m (330 ft) above sea level at its seaward edge.

Who excavated the site?

Claire Cotter directed major excavations in the 1990s under the Western Stone Forts Project.

Is there an entry fee?

Yes—managed by the Office of Public Works; adult admission €5 as of 2025.

Dún Aonghasa stone fort, pointcloud < 1% by The Discovery Programme on Sketchfab

DALTON, J.P., 1928. Who built Dun Aengus?. Journal of the Galway Archaeological and Historical Society, 14(1/2), pp.52-77. ↩︎
Extract from the Lebor Gabála Érenn: The Book of Invasions. Available at: https://www.maryjones.us/ctexts/lebor3.html ↩︎
Quinn, C.P., Kuijt, I., Goodale, N. and Néill, J.Ó., 2019. Along the margins? The later bronze age seascapes of Western Ireland. European Journal of Archaeology, 22(1), pp.48. ↩︎
O’Driscoll, J., 2017. Hillforts in prehistoric Ireland: a costly display of power?. World Archaeology, 49(4), pp.10. ↩︎
Quinn et al., 2019:57. ↩︎
Quinn et al., 2019:59. ↩︎
Quinn et al., 2019:60. ↩︎
O’Driscoll, 2019:11. ↩︎
O’Driscoll, 2019: 12. ↩︎