Yet Rathmarrick, sitting in open pasture near the eastern boundary of Killeen townland, has been considered significant enough to name and map since at least 1838, when it appeared on the first Ordnance Survey six-inch maps of the area. It was still there, still named, on the 1922 revision. What exactly it represents remains an open question.

The site is classified as a possible barrow, a term covering a broad family of prehistoric burial mounds, typically earthen or stone-built, raised over the dead during the Bronze Age or earlier. At Rathmarrick, the structure consists of a raised flat-topped circular platform roughly 6.5 metres across, defined at its outer edge by a stony bank about 1.9 metres wide. The bank survives as a low, irregular scatter of sod-covered earth and stones, rising no more than about half a metre on the interior side, slightly more on the exterior. On the north-western arc, however, the external slope is considerably steeper, reaching 1.6 metres, and both the bank face and the ridge beneath it appear to have been deliberately cut or scarped away at some point, which complicates any straightforward reading of the monument's original form. Whether this was ancient modification, later agricultural interference, or something else entirely is not recorded. The site sits 170 metres south-south-west of Loughnapastia lake, with Nephin Mountain visible to the south-west and the Nephin Beg range stretching along the far horizon, a landscape context that feels entirely in keeping with a monument whose purpose was likely as much about marking place as marking the dead.