Today, none of them can be seen. The cairns, which sit on the dividing line between Knocknagalty and Lyre, have sunk so thoroughly into the rough upland pasture that aerial imagery taken between 2011 and 2013 shows no surface remains whatsoever. What was once solid enough to be recorded on an Ordnance Survey map has been swallowed by the mountain, leaving only coordinates and a database entry to attest to their existence.

Boundary cairns are exactly what they sound like: deliberate accumulations of stone placed to mark the edge of one piece of land and the beginning of another. They are practical rather than ceremonial, though the line between the two was often blurred in an Irish landscape where territory carried considerable social and legal weight. The three cairns on Slievecushnabinnia were not considered significant enough to be recorded on the first edition six-inch Ordnance Survey map of 1840, which is itself telling. By 1897, however, the twenty-five inch edition annotated them simply as 'Mounds', a label that suggests the surveyors recognised something was there without being entirely sure what. The later Cassini edition of the six-inch map depicts one of them as a small circular mound. Two companion cairns lie ten metres and twenty-five metres to the northwest of this one, suggesting the boundary was marked at intervals along the ridge rather than by a single point. The site was compiled into the record by Fiona Rooney and uploaded in November 2021.

Accessing this part of Slievecushnabinnia means crossing rough upland pasture, and the terrain alone requires reasonable footwear and attention to the weather. The mountain sits in an area of south Limerick that sees little visitor traffic, and the absence of any visible surface remains means there is, practically speaking, nothing to see on arrival. What makes the place worth knowing about is precisely that absence, and what it implies about how landscape features disappear. The cartographic record traces a slow fading: noted but unnamed in 1897, reduced to a circular smudge on a later map, and gone entirely by the time a satellite looked down in the early 2010s. If you do walk the boundary line between Knocknagalty and Lyre, bring the relevant OSi map sheet and pay attention to the ground underfoot, where subtle rises in the pasture might be all that remains.