It is called Beal Boru, or Brian Boru's Fort, and the connection to the celebrated High King is tantalising but unconfirmed. What is certain is that the place has a complicated biography, one that involves at least two distinct phases of construction separated by over two centuries, and that the impressive banks and ditches visible today are not quite what they appear to be.

When archaeologist M.J. O'Kelly excavated the site in 1961, he found that its origins lay in a ringfort, the circular enclosed farmstead that was the most common form of high-status rural settlement in early medieval Ireland. The primary bank, roughly one to two metres high and up to 5.7 metres wide, had been faced with stone on the inside and held on the outside by a closely set wooden palisade. A portion of the original fosse, the defensive ditch surrounding the bank, was found intact near the present entrance, measuring 4.5 metres wide and 2.5 metres deep. Coins recovered during the dig dated an internal house to the eleventh century, consistent with the period when Brian Boru held the high kingship from 1002 until his death at the Battle of Clontarf in 1014. The site is thought to have formed part of the wider Kincora complex, the royal seat of the Dal Cais dynasty. After the ringfort was abandoned, a turf layer slowly covered it, and the Annals of the Four Masters record that whatever stood here was raided and demolished in 1116. The story does not end there, however. The high bank, deep fosse, and raised centre with sunken interior that a visitor sees today appear to reflect a later, unfinished attempt, probably in the early thirteenth century, by Norman settlers to build a ringwork, a type of fortified enclosure the Normans used where a full motte and bailey was impractical. That project was never completed and the site was never inhabited in this second phase.

The earthwork sits close to the Shannon and is wooded now, the banks draped in trees that soften what was once a deliberately imposing military silhouette. The fosse and the raised interior are still clearly legible from the northeast approach, giving a sense of the scale of both the early medieval original and the Norman remodelling layered on top of it.