The oval earthwork at Ballaghduff is a rath, the most common type of monument surviving from early medieval Ireland, typically constructed as a defended farmstead enclosure, probably between the sixth and tenth centuries. What gives this particular example a quietly melancholy quality is the gap in its story: the southern and western arc of its external fosse, the defensive ditch that once ran around the outside of the bank, has been entirely swallowed by quarrying activity, leaving only the northern and eastern portions to suggest what the full circuit once looked like.

The earthwork is oval in plan, measuring roughly 28.5 metres north to south and 23.2 metres east to west, and defined by an overgrown earthen bank that remains largely coherent despite sitting in agricultural land. A fosse is simply the ditch thrown up alongside a bank during construction, the soil from it typically forming the bank itself. Several breaks visible in the bank today appear to be relatively recent, probably the result of farm access over the years rather than deliberate clearance in any earlier period. The site occupies a slight rise in the undulating ground around it, which would have given its original occupants a modest but practical vantage over the surrounding landscape.