After Hugh de Lacy granted Dunboyne to William le Petit, the latter established this earthwork fortification as the administrative heart of his manor, possibly adapting an earlier Irish rath that already occupied the site. The original earth and timber castle served its purpose until around 1475, when it was superseded by a stone tower house that better suited the changing military and social needs of the late medieval period.

Archaeological excavations between 2001 and 2005 have revealed the impressive scale of this Norman stronghold. The castle’s defensive ditch was a formidable barrier, measuring up to 8.5 metres wide and 4.5 metres deep, its waterlogged depths preserving layers of brushwood and timber that speak to its twelfth or thirteenth century origins. The finds paint a picture of daily life within the enclosure; stick pins, keys, metal tools, and pottery sherds, including exotic French imports alongside local Leinster cooking ware. The discovery of ash bowls in the basal layers and evidence of a possible gatehouse structure with corner posts and linking timbers at the eastern entrance show the sophistication of the site’s construction.

The interior of the enclosure reveals multiple phases of occupation spanning centuries. A prehistoric ring ditch was uncovered beneath the medieval layers, whilst features from the Norman period include what may have been a grain drying kiln, a circular structure marked by two concentric rings of stake holes that could have been a roundhouse or storage building, and a raised rectangular structure possibly used as a granary. Stone revetments with a battered slope lined portions of the inner face of the ditch, and rubble filled foundation trenches suggest that masonry buildings once stood within the enclosure. Though much of the site was disturbed by the construction of an eighteenth century house and its cellars, the archaeological evidence confirms this was once a thriving centre of Norman power in medieval Ireland.