That absence is itself a clue. The feature only became visible to researchers through aerial imagery in the twenty-first century, and it may represent not one ancient site but two overlapping ones, their boundaries blurred by time and wet ground.

The site belongs to a category of prehistoric monument known as a fulacht fia, a term used for the horseshoe-shaped mounds of burnt and fire-cracked stone that appear in their thousands across Ireland, most commonly near water sources. The leading interpretation is that these were outdoor cooking sites, where stones were heated in a fire and then dropped into a water-filled trough to bring it to boiling point. The marshy setting here would have provided exactly the kind of waterlogged ground that fulachtaí fia typically favour. This particular example, recorded under the reference LI028-174, sits immediately beside a second recorded fulacht fia, LI028-089, and it is an open question among researchers whether the two are in fact a single monument that has been catalogued twice. The site was first identified in 1986 by Jerry McMahon of Ardagh, a member of the Newcastle Historical Society, who brought it to the attention of the Archaeological Survey of Ireland through correspondence. Its absence from both the 1840 and 1897 Ordnance Survey editions adds to the uncertainty around its extent and character. Edmond O'Donovan compiled the formal record, uploaded in September 2020.

The mound is visible on satellite imagery and was captured on Google Street View in September 2019, seen from the R523 looking north-west. The townland boundary with Ballylin runs approximately sixty metres to the north-west of the site. Visitors approaching along the R523 should bear in mind that the feature sits in working agricultural land, low-lying and prone to waterlogging, which makes it easier to spot as a subtle rise in the pasture than to reach on foot. The slight elevation of the mound against the flat surrounding ground is most legible from the road rather than up close, and the wet conditions underfoot around Ballylin Hill persist through much of the year.