The rock is no monument in the conventional sense, no enclosure or structure to frame it, just a hogbacked outcrop sitting in open pasture with the Kealduff river valley stretching away to the north-east and Lough Brin visible beyond. What makes it quietly arresting is the sheer density of marks worked into a decorated surface measuring roughly 2.25 metres by 1.3 metres: nineteen single cupmarks, nine cup-and-ring motifs, seven cupmarks with partial rings, meandering grooves, and a long radial groove that serves as an informal organising line, with most of the carvings clustered to its south and west.

Cupmarks are among the most common and least understood elements of prehistoric rock art, essentially small circular depressions pecked into stone, sometimes left plain and sometimes surrounded by one or more concentric rings. Here, they range from around 4 to 5.5 centimetres in diameter and only a few millimetres deep, which gives a sense of how painstaking the work was and how vulnerable to weathering. The motifs at Derrynablaha appear in the archaeological record as early as Anati's 1963 survey, and were later documented in O'Sullivan and Sheehan's 1996 survey of the Iveragh Peninsula. A natural rock fissure runs through the surface and seems to have influenced how the carvings were laid out, with the decorated field keeping largely to one side of it. At the boulder's north-west corner, a long pocked groove follows the very edge of the rock, as though someone once felt the need to mark its boundary as well as its face.

The boulder sits in upland heath pasture with the ground rising steeply to the north-west and a rugged mountain landscape pressing in from the south-west. The carvings are visible, though lichens cover much of the surface, and lower-angled light tends to bring the shallow motifs into sharper relief. A 3D model of the stone is available online at skfb.ly/6yKAx, which gives a useful sense of the surface geometry before visiting.