Dún Ailinne is connected with the Leinster dynasty. Legend has it that this was a place where Fionn Mac Cumhaill and the Fianna once lived. The oldest references connect Leinster (Laigin) to the descendants of Labraid Loingsech and Lóegaire Lorc. It has been suggested that the name Laigin comes from the word láigen, meaning "spear". The dynasties of Uí Garrchon, Uí Máil, Uí Failge, Uí Bairrche, Uí Dúnlainge, and Uí Chennselaig (Kinsella) ruled Leinster after the fifth century. At its peak, their realm, the cóiced Laigen or "fifth" of Leinster, encompassed the whole of southeastern Ireland between the Shannon and the Boyne. We know that Dún Ailinne eventually became the headquarters for the powerful Uí Dúnlainge, established after Murchad of Uí Dúnlainge defeated the invading Uí Néill in the fierce battle of 721 and took control of Kildare's plains.

This mysterious place covers a huge tract of land. The hilltop bank alone encompasses about thirty-seven acres. Earliest documents confirm that it was built around the birth of Christ and was mostly abandoned by the time the early Christian settlement at nearby Old Kilcullen was established in the sixth century.

The question remains as to whether or not ancient Dún Ailinne was permanently occupied as a settlement or used only for ceremonial purposes.

The alterations to the landscape itself may answer this. Examination of the enclosure shows that the bank's ditch is inside, the same as Emain Macha and central Tara. If these sites were typical hill-forts, the ditches would be outside the banks in keeping with usual methods of defensive construction. The only types of circular earthworks with ditches inside their banks are the henges of the British Late Neolithic period, which are definitely proven to have been ritual sites.

In addition, there is nowhere inside Dún Ailinne that gives a complete view of its surroundings, as a hill-fort would need to see in all directions. Furthermore, there is no disctinct evidence of any typical internal hill-fort features such as palisades or any significant findings of weaponry artifacts.

Archaeologists have found some signs of occupation in the low mound just to the northeast of the embankment. Charcoal, bone and refuse were found, more of it with deeper excavation. In fact, the mound consists mainly of debris and was probably once surrounded by a fence or some sort of enclosure. Artifacts found here include small bits of bronze and a few glass beads that can't be specifically dated but are probably from early centuries A.D. This low mound is the only occupation area found at Dun Ailinne to date.

Digs during the 60's and 70's discovered three phases of construction involving central timber enclosures in different patterns, mostly concentric and circular. The earliest was a figure eight structure with one large circle, an annex to the south, and an elaborate entranceway. The next phase was a circle of timbers and a smaller, closed circle. The last one must have hosted much ceremonial feasting based on the plentiful animal bones found at that level.

Excavations at Dún Ailinne led by Bernard Wailes from 1968-1974 found no breaks between the phases of construction. This probably means that each previous phase was dismantled before the next stage of building.

The finding of a rare La Tene style (Iron Age) sword in one of the trenches from Phase 3 deepens the mysterious aura of this place. We can only imagine what went on at this site two thousand years ago. Recent quarrying by Roadstone Dublin has drastically altered the west side of the site to the point where, despite promises of restoration, it may never be the same.

Sources:

A glance at the plan of Dun Ailinne

Hillforts of the Leinster Dynasty

The MacMillan Atlas of Irish History, edited by Seán Duffy, MacMillan Press, 1997

The Oxford Companion to Irish History, edited by S.J. Connolly, Oxford University Press, 1998