Somewhere on an east-facing slope at Grenagh in County Cork, a ringfort once stood. A rath, to use the more specific Irish term, is a type of enclosed farmstead common throughout early medieval Ireland, typically consisting of a roughly circular earthen bank and ditch enclosing a domestic space. This one measured around fifty metres in diameter. Today, the ground has been levelled and cultivated into tillage land, leaving no visible surface trace of what was once there.

The earliest cartographic evidence for the site comes from the Ordnance Survey six-inch map of 1842, which records it as a hachured circular enclosure, the hatching being the standard surveying convention for indicating a raised earthwork. By the time the 1904 and 1938 editions of the same map series were produced, the enclosure itself had gone, but a curved arc of its original outline, running roughly north-northwest to southeast, had been absorbed into the local field fence system. Farmers, without necessarily knowing it, had preserved the ghost of the ringfort in the lines of their own boundaries. That arc, too, has since disappeared, leaving the landscape with no outward sign that the site ever existed.