The Ballinlug stone, the earliest recorded example of rock art in County Westmeath, is a block of millstone grit, a coarse-grained sandstone, measuring roughly 87 by 48 centimetres. On its face, a prehistoric carver incised three concentric rings围绕 a central cup-mark, the whole motif less than 30 centimetres across. Radial grooves run outward from the cup through the rings, and a cluster of smaller concavities sits in one corner, though whether those are deliberate cup-marks or natural solution hollows remains uncertain. Notably, the stone is not local; millstone grit is foreign to this part of Westmeath, which raises questions about how it arrived and what significance it once held.

When James Tuite wrote about it in 1913, he found it already embedded in a roadside wall along the Ballymahon Road, placed there by a mason who had set the carved face inwards. The stone had been lifted from an adjoining field at some earlier point and pressed into ordinary service as building material. When the wall was later rebuilt, the carved side was turned outward by chance, which is presumably how Tuite came to notice it at all. After he documented it, a Mr. Donohoe, who lived in a farmhouse on the opposite side of the road, removed the stone and placed it beside the doorway of his cottage. By the time a researcher located it again in August 2009, it had migrated once more, coming to rest close to its original findspot but buried in dense undergrowth on top of a rubble bank, entirely covered in moss. Cup-and-ring rock art of this kind, where circular grooves are cut around a central hollow, is a recurring motif in prehistoric Europe, though its precise meaning remains unknown; the Ballinlug stone is unusual partly because such carvings are rare in the Irish midlands.