The Ordnance Survey's six-inch map of 1837 recorded nothing here, yet by the time the revised edition appeared in 1913, a subrectangular feature had been plotted: roughly thirty metres east to west and twenty-five metres north to south, defined on its western and northern sides by an L-shaped bank, and open to the south.

The 1913 map uses hachuring, a technique of short parallel lines used to indicate raised earthworks, to mark the bank. That bank has since been levelled, leaving no obvious mound above the surrounding grass. What remains is something more subtle: a slightly raised outline, the enclosure's footprint still just detectable underfoot and in the lay of the land. The eastern side coincides with a field boundary that also serves as a townland boundary, a detail that sometimes suggests older land divisions being absorbed into, or preserved by, later agricultural arrangements. The enclosure's original function is not recorded, and without excavation, any interpretation would be guesswork.

The site sits at the break of slope, the point where a hillside begins to level off, a position that recurs frequently in the siting of early enclosures across Ireland, perhaps for drainage, visibility, or the practical business of managing livestock. At Barnacoghil, the feature is not signposted or formally presented; it survives simply as a slight irregularity in a working pasture field, the kind of thing that becomes visible only once you know to look for it.