Seven metres across and hollow at the centre, it is one of five unclassified cairns clustered near a larger cairn on the same hilltop, the whole arrangement suggesting a landscape that was once carefully, deliberately marked out, even if the precise purpose of each structure has long since become unclear.

A cairn, in the broadest sense, is a human-made mound of stones, and examples across Ireland range from elaborate megalithic passage tombs to simple waymarkers. The cairns on Spinans Hill fall into neither obvious category; they remain unclassified, which is itself significant. They sit within Spinans Hill hillfort, which is in turn embedded within a larger hillfort complex straddling the Wicklow uplands, a landscape of layered prehistoric activity. This particular cairn lies roughly 30 metres to the north-north-east of the larger central cairn, and consists of loose stone with some small boulders mixed in. The hollow at its centre may be the result of long-ago disturbance or partial collapse, a common fate for unprotected stone monuments in upland pasture. The site is recorded under the name Grogan no. 1 in the SMR file, pointing to fieldwork that documented this concentration of monuments before much of the surrounding area received systematic survey coverage.

The summit of Spinans Hill offers what the record describes as extensive views in all directions, which is worth bearing in mind when considering why so many monuments were placed here. Whether those cairns marked territory, commemorated the dead, or served some other communal function, the hilltop clearly mattered to the people who shaped it. The hollow at the centre of this otherwise unremarkable pile of stones is perhaps the detail that lingers longest, a small absence where something may once have been.