This one is remarkable for what does not. A rath, or earthwork ringfort, the type of circular enclosed settlement built across Ireland from the early medieval period into the first millennium, is recorded at Terrygeely in County Monaghan on only a single historical map, and has since effectively vanished, leaving no visible trace on the ground or in aerial photography.

The sole evidence for this enclosure comes from McCrea's map of County Monaghan, published in 1793. That map places the feature on a slight rise in low-lying ground, set between drumlins to the west and east. Drumlins, the elongated hills of glacially deposited material that ripple across this part of Ulster, would have made such a rise a reasonably practical spot for settlement, visible across the surrounding boggy hollows. But whatever earthwork once occupied that position has left no discernible imprint. Modern aerial imagery reveals nothing, and the precise location of the site cannot now be confirmed. It exists, in effect, as a cartographic ghost, recorded once and never corroborated.