What makes it unusual is its scale relative to its surroundings: a central mound roughly six metres across and over three metres high at its southern end, encircled by a fosse, which is a wide defensive or ceremonial ditch, and an outer bank of earth and stone. The whole structure measures around 37 metres in diameter, which is a considerable footprint for something that registers so little in the local landscape.

Barrows of this kind, sometimes called ring barrows, were built during the Bronze Age as funerary monuments, though their exact ritual use varied. The combination of central mound, encircling ditch, and outer bank is a form found across Ireland, and the example at Garrauncreen survives in fair condition despite centuries of agricultural activity. The outer bank has been largely lost, surviving for only about four metres on the north-western side, and a pronounced depression at the centre of the mound points to earlier disturbance, whether by antiquarians, treasure-seekers, or simple agricultural encroachment over the years. About 220 metres to the east lies a separate cairn, a stone-built funerary monument, suggesting this part of Galway once held a cluster of prehistoric burial activity rather than a single isolated structure.