At Boughill in County Monaghan, there is a ringfort, or rath, recorded in the books, a circular earthwork enclosure of the kind that once dotted the Irish countryside in their thousands, typically serving as farmsteads during the early medieval period. The problem is that nobody can say with any confidence where exactly it is, and nothing at ground level suggests it was ever there at all.

The sole evidence for this enclosure comes from McCrea's Map of County Monaghan, drawn in 1793. On that map, an enclosure is marked in this general area of Boughill, on what is described as a level, low-lying stretch of land. No subsequent cartographic survey repeated the marking, and no trace of a bank, ditch, or raised feature has been identified on the ground. Whether McCrea recorded something that was already fading in his own time, or whether the feature was lost to later land improvement and drainage, the landscape today gives nothing away. The precise location remains unknown.