The outer enclosure, with its fosse (a defensive ditch) and raised bank, belongs to a rath, the ringfort type that dots the Irish countryside as a legacy of early medieval settlement. What makes this site quietly odd is the layering: eighteenth-century friars, evading the Penal Laws, chose to build their refuge inside a structure that predated them by perhaps a thousand years, and the reason they may have done so had nothing to do with defence or elevation. It was, apparently, the underground.

Around 1713, four houses of refuge for friars were established in the Diocese of Meath, and the building at Friarstown was likely one of them. The site sits at the southern end of a north-to-south ridge, set within what was then good pasture, with open views to the west, south, and east. Two small raths had been raised on this ridge, and the friary was constructed within one of them. The probable reason for that unusual choice was the presence of a souterrain beneath the site. A souterrain is an underground passage or chamber, typically built of dry stone, that served in earlier centuries as a place of storage or concealment. At Friarstown, the souterrain had a corbelled roof, meaning it was sealed with overlapping courses of stone rather than a flat lintel, though that roof has since collapsed. For friars living under legal prohibition, a ready-made underground hiding place would have been a considerable practical asset. The refuge does not seem to have lasted long. Friarstown was probably among the houses demolished by British authorities in 1732.

The masonry that survives above ground is modest but legible. Grass-covered stone footings of a rectangular structure remain at the southern end of the enclosure, with the north-west corner standing to roughly two metres and part of the east wall reaching about one and a half metres. The walls are built in horizontal courses of undressed stone bonded with mortar, and a short internal wall projects from the north side to form two bays. Two original causeways across the fosse, one to the west and one to the south, are still traceable, though the eastern side of the enclosure has largely been absorbed into a modern field boundary.