It is not visible as earthwork or masonry; the only reason we know it is there at all is because, under the right conditions, growing crops betray what the soil remembers. The buried ditch, or fosse, that once defined this enclosure causes the vegetation above it to grow differently, and on 15 July 1991, an aerial photograph caught those differences clearly enough to outline most of the circuit.

The photograph in question, reference GB91.DZ.04, revealed the cropmark of an incomplete oval defined by the fosse, traceable from the south-east around through the south to the north-west. A cropmark forms when buried features, such as a filled-in ditch or the remains of a wall, affect the moisture and nutrients available to crops above them, producing variations in growth rate or colour that become legible from the air, particularly in dry summers. The Barrowmount enclosure is substantial in scale, placing it in the category of large enclosures that in an Irish context can be associated with a range of prehistoric or early medieval functions, from settlement to ritual use, though nothing in the available record pins this one to a specific period or purpose. What the photograph also shows is a patch of darker staining inside the enclosure, near the fosse in its south-western quadrant, which may point to small-scale quarrying activity at some point in the site's history. By 1991, a field boundary already cut roughly east to west through the centre of the enclosure, and two houses had been built within or immediately adjacent to its footprint, one just east of the south-eastern sector, another intruding into the north-eastern arc.