A ringfort, or rath, was a roughly circular enclosure defined by an earthen bank and ditch, built during the early medieval period as a farmstead or place of settlement. This one, around thirty-five metres across, was recorded as a circular enclosure on the Ordnance Survey six-inch map of 1842. Sometime around 1865, according to local information, it was levelled, most likely to improve the land for agriculture. The physical structure was removed, but the archaeology remained.

What makes the site quietly remarkable is how it continues to surface. When the field is ploughed or when crops grow, differential soil colour betrays the position of the old earthworks. This kind of crop or soil mark occurs because disturbed archaeological deposits retain moisture, organic material, or compaction differently from the surrounding undisturbed ground. The result, visible from the right angle at the right time of year, is a ghostly echo of the original enclosure, still roughly circular, still roughly where the map recorded it over a hundred and eighty years ago. The rath at Coolyrahilly is, in practical terms, gone. In another sense, it keeps reappearing.