Yet the very modesty of what remains on the ground is part of what makes this site worth pausing over. A ringfort, or rath, is a circular earthwork enclosure, typically dating from the early medieval period and used as a defended farmstead. At Rathduff, the enclosure was once substantial enough to be mapped three separate times across the nineteenth and early twentieth centuries, and substantial enough, too, to have been deliberately flattened within living memory.

Ordnance Survey maps from 1842, 1904, and 1938 all show a circular enclosure of around 40 metres in diameter. The 1904 map goes further, depicting an inner bank of roughly 20 metres in diameter as well, suggesting a bivallate ringfort, one with two concentric earthen banks rather than the more common single bank. When the Office of Public Works recorded the site in 1965, both banks were still standing: the inner bank rose to an internal height of around six feet, the outer to three feet externally, with a fosse, a defensive ditch, running between them. Sometime around 1973, according to local information, the monument was levelled. The OS maps, the 1965 measurements, and what little the ground now shows are the only record of something that had endured, in some form, for perhaps a thousand years before it did not.

The site is not entirely invisible. A roughly circular area of approximately 27 metres east to west and 24 metres north to south can still be made out as a low rise in the pasture, and a slight secondary rise about five metres beyond it may represent the remnant of the outer bank. Aerial photography by Dr D.D.C. Pochin Mould captured the site as a clear crop mark, the kind of ghostly impression that shows up when differential soil moisture causes overlying vegetation to grow unevenly above buried or disturbed ground. From the air, what is nearly gone at ground level becomes, briefly, legible again.