What it skirts is an ancient earthen enclosure in the townland of Duninga, a roughly circular rath, the term used for a ringfort, a type of enclosed settlement common in early medieval Ireland, measuring around ninety metres across and defined by a bank or scarp running from west through north to south, with a gap opening in the southwest. Inside, historical maps record a large hollow, approximately fifty metres in diameter, whose purpose remains unexplained.

The first Ordnance Survey mapping of 1839 captured only the northern portion of the monument, showing a curving bank within woodland, the full circuit not yet documented. By the 1900 revision, the near-complete enclosure had been recorded more thoroughly. The site sits at the eastern end of a linear earthwork known as Rathduff Trench, a feature that runs roughly east to west just outside the northern edge of the enclosure. Writing in 1839, a Reverend W. K. Boroughs described the discovery, made some years earlier, of two stone-lined cist graves, each neatly flagged at the bottom and sides, found about sixty centimetres below the surface. One was the grave of a child, the other of an adult man. Both contained earthen vessels of baked clay, which were broken during the uncovering. The bones showed no signs of burning. Boroughs regarded the fort as part of a chain of monuments that once marked the boundary between two significant ancient territories, a reading that the alignment of the Rathduff Trench tends to support. Later, according to a 2008 local study, the monument was quarried into for gravel, a fate that accounts for some of the damage visible today.