The site came to light during excavations in 2003, when only the south-east corner of the feature, known as enclosure 4, fell within the road corridor. What made the investigation immediately complicated was the evidence itself: radiocarbon dates from the fills of the fosse, the enclosure ditch, pointed to both the Iron Age and the early medieval period. The excavator ultimately favoured an early medieval date, partly on the basis of a grain sample dominated by oats, a crop more characteristic of that later period than of the Iron Age. A fosse, to borrow a word from earthwork archaeology, is simply a ditch dug to define or defend an enclosed area; here it ran roughly 1.7 metres wide and 0.6 metres deep, extending eastward for seven metres before turning sharply north for a further fifteen.

The enclosure held one particularly unusual detail. Close to the south-east corner, within the interior, excavators found a cremation pit burial, a relatively rare feature within an enclosure of this kind and one that raises quiet questions about how the space was used and by whom. Further investigation in 2005 extended the picture considerably. Geophysical survey using gradiometry, a technique that detects buried features by measuring variations in the earth's magnetic field, combined with test-trenching to the west of the original road corridor, confirmed that the enclosure continued beyond the excavated area. The fuller outline resolved into a rectangular form approximately 22 metres north to south and around 18 metres east to west, its ditch slightly narrower in this section at roughly 1.6 metres wide. A date obtained from the fill of this outer section calibrated to between approximately AD 780 and 979, placing it firmly in the early medieval period, the era in Irish history associated with ringforts, monastic settlements, and the small farming communities that shaped much of the landscape we see today.