That absence is precisely the point. A small circular enclosure, roughly twenty metres across, was recorded on the first edition Ordnance Survey six-inch map of 1839, but by the time the 1900 revision was carried out, it had vanished from the landscape entirely. Sometime in those intervening six decades, the feature was levelled, leaving no visible trace at ground level.

Enclosures of this kind, typically earthen ringworks that may once have served as farmsteads, livestock enclosures, or sites of early settlement, are found throughout Ireland and represent some of the oldest organised land use in the country. At Lisnalea, the 1839 mapping caught it just in time. The first edition OS six-inch survey, carried out across Ireland in the 1820s and 1830s, recorded countless earthworks and field monuments that have since been destroyed through agriculture, drainage, and land improvement. The Lisnalea enclosure appears to be one of those casualties, cleared as part of the broader reclamation of upland and marginal ground that intensified during the nineteenth century. What the site was originally used for, and how old it was, is no longer recoverable from what remains.