It is a bullaun stone, a type of carved or naturally hollowed rock found at early medieval ecclesiastical sites across Ireland. The defining feature is the basin worn or cut into its upper face, a shallow cup-shaped depression that has accumulated rainwater, folklore, and centuries of quiet use. The Glendalough example is modest in scale but precise in its dimensions: roughly half a metre square, with a single cylindrical basin measuring about 26 centimetres across and 16 centimetres deep, its sides vertical and its bottom slightly concave.

The stone was recorded by Healy in 1972, who noted those specific measurements and described the basin's cylindrical form with some care. Bullaun stones are generally associated with early Christian monastic settlements, where they may have served liturgical, medicinal, or votive purposes, though their exact function remains debated. Some were used for grinding; others accumulated associations with healing or cursing over time, with the collected water considered to have curative properties. The Sevenchurches site, the local name for the monastic complex at Glendalough founded by St Kevin in the sixth century, contains several early ecclesiastical structures, and this unassuming stone sits in the shadow of one of them, just beyond the church wall.