Both mounds have sunk so far into the hillside that they are no longer visible at surface level, which gives the site an odd quality: monuments that were once substantial enough to be formally recorded are now entirely absorbed by the landscape.

Cairns are prehistoric burial mounds, typically constructed from heaped stone rather than earth, and they appear across upland Ireland in considerable numbers. The two at Glencap Commons were documented in the Ordnance Survey letters of 1928, compiled by O'Flanagan, which captured many local antiquities before they deteriorated further or were forgotten entirely. At the time of that recording, the larger of the two measured roughly sixteen metres in diameter and stood approximately 2.7 metres high, with the smaller cairn, around 9.4 metres across, lying about 25 metres to the north. These are not insignificant dimensions, particularly for the larger mound, which would once have been a conspicuous feature of the hillside. The position overlooking the Rocky Valley ravine suggests a deliberate choice of location, as elevated or visually commanding spots were frequently selected for such monuments, possibly to mark territory, commemorate the dead, or simply to be seen across a wide area.