Large boulders or a rock outcrop break the surface at its north-western edge, and the whole thing measures roughly eighteen metres across in each direction, a sub-rectangular shape that feels too deliberate to be purely geological, yet too ambiguous to have earned a firm classification on any edition of the historic Ordnance Survey maps. It was never marked as an antiquity. That absence is part of what makes it curious.

The most likely explanation is that this is the remnant of a small barrow, the term for a prehistoric burial mound, raised on a natural rise in the landscape. At some later point, probably during the formal landscaping of the nearby Kilranelagh House demesne, the mound appears to have been absorbed into the estate's ornamental scheme. By the time the six-inch Ordnance Survey map was produced in 1838, the spot was recorded simply as a small grove of trees standing on poorly drained ground within the demesne lands, roughly 240 metres to the north-east of the house itself. The twenty-five-inch map later showed the same area as an enclosure with trees inside, preserving the outline without any suggestion that something older might lie underneath. Whether the estate gardeners recognised what they were incorporating into their planting, or simply found a convenient hillock, is not recorded.