A decorated boulder emerged from the south-eastern slope of Kill hill in County Kildare not through excavation but through clearance work, when a rough arc of boulders about twenty metres in diameter was removed from the hillside in 1990. Underneath, or within that scatter, lay a slab of green Silurian slate, a metamorphic rock formed during the Silurian period roughly 440 million years ago, measuring just over a metre and a half in length. Its two surfaces had been carefully worked by hand at some point in prehistory, and what they carry is unusually elaborate by Irish standards.

The decoration belongs to the cup-and-ring tradition, a form of prehistoric rock art found across Atlantic Europe and Ireland, in which shallow depressions, or cupmarks, are pecked into stone surfaces, often surrounded by concentric rings. On this particular boulder, the motifs are complex rather than simple: two large central compositions combine cupmarks with alternating bands of small pecked cups and rings, while other areas of the stone carry ringed cups enclosed by further bands of small cups, single ringed cupmarks, and, on one, radial grooves extending outward from the centre. The remainder of one surface is covered in small shallow cupmarks. The surrounding arc of boulders, made largely of the same Silurian slate with some red conglomerate mixed in, may have been the remnants of a cairn, a burial or ritual mound of heaped stone, suggesting the decorated boulder once sat within a more structured prehistoric context. The site lies about five hundred metres east of a hilltop enclosure on Kill hill, a proximity that may be significant, though what relationship existed between the two features is unknown. The stone was removed to the National Museum of Ireland in 1993, so the hillside itself no longer holds what made it remarkable.