In gently undulating pastureland at Kilglass in County Galway, a roughly circular enclosure roughly twenty metres in diameter was recorded on the first edition of the Ordnance Survey six-inch map, one of the great nineteenth-century efforts to document the Irish landscape in systematic detail. Today, almost nothing of it can be seen. A very slight rise in ground level along its north-eastern limits is all that remains above the surface, a faint ripple in the grass that most walkers would step over without a second thought.

Enclosures of this kind are among the most common, and most enigmatic, categories of early monument in Ireland. The term covers a broad range of circular or near-circular earthworks, some of which served as settlement enclosures, others as field boundaries or ceremonial spaces, and many of which resist confident interpretation entirely. At around twenty metres across, the Kilglass example is modest in scale. Its origins are unknown, and without excavation, they are likely to remain so. What the first edition OS map captured, probably in the mid-nineteenth century, was presumably a more legible earthwork than survives now, its gradual disappearance into the pasture a result of the ordinary processes of agriculture and time working on a feature that was already ancient when it was first committed to cartography.