Once a prehistoric cairn, a type of ancient stone heap typically raised over a burial or as a landscape marker, it was later pressed into service by the Ordnance Survey as a trigonometrical station, meaning the surveyors used it as a fixed reference point for calculating distances and elevations across the surrounding terrain. The fact that a structure built by people in prehistory was still prominent enough in the nineteenth century to anchor a modern mapping exercise says something about the stubborn persistence of these features in the Irish uplands.

The cairn sits at the southern edge of a conifer plantation in the townland of Ballintober, immediately west of the boundary with the neighbouring townland of Killeen. Its clearest documentary appearances come from two Ordnance Survey Ireland editions. The 1897 twenty-five-inch map marks it explicitly as a trigonometrical station, indicating it was actively used in survey work at that time. An earlier Cassini edition of the six-inch map annotates it simply as "Carn" and depicts a roughly circular mound at the spot height of 1,243 feet, which is 378 metres. By the time Digital Globe captured ortho-imagery of the area between 2011 and 2013, only a faint trace of the cairn remained visible, suggesting that the structure has been gradually obscured or disturbed, likely by the encroaching plantation or by the general degradation that affects upland sites over time. The record was compiled by Martin Fitzpatrick and uploaded in September 2021.

Accessing this kind of upland site in County Limerick requires some patience with the landscape. The southern edge of a conifer plantation is rarely the most straightforward terrain to navigate, and the boundary between Ballintober and Killeen is not marked by any obvious feature on the ground. Visiting with a current Ordnance Survey map or a GPS-enabled device cross-referenced against the historic six-inch mapping would give the best chance of locating what remains. Given that even satellite imagery from the early 2010s shows only a faint trace, expectations should be modest. What survives is less a dramatic monument than a subtle irregularity in the ground, the kind of feature that rewards close attention rather than a casual glance.