That uncertainty is itself the most interesting thing about it. Unlike the thousands of raths scattered across Ireland whose earthen banks remain clearly visible as circular raised enclosures in fields and pasture, the one recorded at Lisarrilly has left no trace that anyone can presently find. The pasture shows nothing. The precise location is unknown.

The sole evidence for this structure comes from McCrea's Map of County Monaghan, surveyed in 1793, which marks a circular earthwork enclosure at this spot on top of a drumlin, the smooth elongated hill formed from glacial deposits that give Monaghan its famously lumpy landscape. A rath, to use the Irish term, was typically a farmstead enclosed by one or more earthen banks and ditches, home to an early medieval family of some local standing. They were built in their thousands between roughly the sixth and twelfth centuries and remain among the most common field monuments in Ireland. The Lisarrilly example, if it survived into the late eighteenth century in a form legible to a cartographer, has since vanished, whether through agricultural levelling, gradual erosion, or simply the difficulty of relocating a feature on an unmarked drumlin top without further survey work.