It is overgrown with trees now, conspicuous enough from aerial imagery as a dark, vegetated disc in otherwise open pasture, but it left no trace whatsoever on the first detailed Ordnance Survey maps of the area. That absence is itself part of the puzzle.

The feature does not appear on the 1840 edition of the Ordnance Survey six-inch map, the great mid-nineteenth century survey that recorded Ireland's landscape in remarkable detail. By the time the twenty-five inch edition was produced in 1897, however, it is clearly marked as a circular-shaped hollow, already hemmed in by field walls running from the south-east, around through the west, and back to the north-east. The gap between those two surveys is significant. If the hollow predated 1840 and was simply missed, that would be unusual given the thoroughness of the earlier surveyors. More likely, it came into being sometime in the second half of the nineteenth century, though a post-1700 origin has been suggested. The working hypothesis, compiled by Martin Fitzpatrick and uploaded to the record in November 2021, is that it may be the remains of a quarry, the kind of small, localised extraction pit that farmers once dug to source limestone or other material for building and for spreading on fields to improve soil. Such quarries were common across rural Ireland and rarely merited formal documentation. The site lies about 190 metres west of a watercourse that forms the boundary between Ruppulagh and the neighbouring townland of Ballintober.

The hollow is on private farmland and sits in pasture, so any visit would require permission from the landowner. For those researching the area, the most accessible view is via Google Earth or Digital Globe orthoimages from the 2011 to 2013 period, where the ring of trees makes the feature easy to identify from above. On the ground, the enclosing field walls are the clearest physical indicator of something deliberate and bounded in an otherwise ordinary agricultural landscape.