They are modest things: each roughly five centimetres across and less than three centimetres deep. Without knowing what to look for, you might walk past them entirely. With that knowledge, they become something stranger, a quiet signal from prehistory with no label and no clear explanation.

Cupmarks are among the most widespread and least understood forms of prehistoric rock art found across Ireland and Britain. They are exactly what they sound like: shallow, rounded hollows ground or pecked into stone surfaces, usually by hand. When they were made, by whom, and for what purpose remains genuinely uncertain. Ritual use is the most common suggestion, but the evidence is largely circumstantial. The Glannafeen stone sits on a steep east-facing slope at a break in the terrain, a natural shelf of sorts, with the southern reach of Lough Hyne visible below. The boulder itself is substantial, measuring just under two metres in length, and the two cupmarks appear on its uppermost face. The location is not incidental. Many cupmarked stones across Ireland occupy elevated or visually commanding positions, and this one, looking out over one of Ireland's few saltwater lakes, fits that pattern without being reducible to it.

Lough Hyne itself is a marine nature reserve, sheltered and tidally connected to the Atlantic by a narrow channel, and the hillside above it is rough and unimproved. The stone sits somewhere in that landscape, in pasture on the slope, though finding it without prior knowledge of the exact location would take patience and a good eye for subtlety in the terrain.