The excavation at Earlsrath in County Kilkenny, carried out in 2006 ahead of works on the N9/N10 Waterford to Kilcullen route, uncovered only part of an enclosure, and that partial picture is itself part of what makes it interesting. Archaeologists exposed the western half of a subcircular enclosure roughly 27 to 28 metres in diameter, defined by a V-shaped fosse, the term for a defensive or boundary ditch, measuring 2.6 metres wide and up to 1.2 metres deep. The site continued eastward beyond the excavation boundary, meaning the full extent of what once stood here was never fully revealed.

Radiocarbon dating placed the initial use of the main fosse in the period between approximately 419 and 535 AD, placing it in the post-Roman, early medieval horizon when enclosed settlements, often associated with farming households or minor lordly sites, were being established across Ireland. A later date, between roughly 885 and 990 AD, came from one of the lower fills within the same fosse, suggesting the feature was accumulating material well into the Viking Age. Two smaller fosses extended from the main enclosure to the north-west, running beyond the limits of what could be excavated. A scatter of pits in the same area were read as rubbish deposits, the kind of domestic refuse that, unglamorous as it sounds, often tells archaeologists more about daily life than any monument does. Stranger still was the discovery, in the north-west quadrant, of two pits dating to the Early Neolithic, thousands of years older than the enclosure itself, suggesting that people had been drawn to this ground long before the ditch was ever cut.