What makes this particular site quietly compelling is that it exists more convincingly on paper than it does on the ground. The earthwork at Grig has effectively vanished, leaving its clearest trace not in the soil but in a two-hundred-year-old map.

The evidence for the fort's existence comes from an estate map of the Barony of Cremorne surveyed by Brownrigg and Longfield in 1790, now held in the National Library of Ireland. On that map, a circular earthwork is clearly depicted on the drumlin summit, a drumlin being one of the smooth, elongated hills of glacial debris that define so much of the Monaghan landscape. Such elevated positions were favoured sites for raths, offering visibility across the surrounding terrain. By the time aerial photography examined the site in 1995, 2000, and again in 2005, no archaeological features remained visible. Later satellite imagery confirmed the same absence. Whatever earthworks once crowned the hill have since been levelled, most likely by generations of agricultural improvement.

The 1790 map therefore serves as an inadvertent archaeological record, preserving the outline of something that farming eventually erased. It is a reminder that the distribution of surviving ringforts across Ireland represents only a fraction of those that once existed, and that many more vanished quietly over the intervening centuries, documented, if at all, only by the occasional surveyor who happened to pass through.