This one exists almost entirely as a ghost in a photograph. The ringfort at Knockbarry in north County Cork is known primarily through a cropmark, a phenomenon where buried earthworks cause overlying crops or grass to grow at subtly different rates, producing patterns that only become legible from the air. What the aerial photograph reveals is the outline of a rath, the Irish term for a ringfort, showing a bank and an external fosse, which is a defensive ditch, running from south to northwest, before the whole thing is cut off on its northern side by a later field fence running east to west.

Ringforts are among the most common monument types in the Irish landscape, with estimates running into the tens of thousands across the island. Most date from the early medieval period, roughly the fifth to the twelfth centuries, and functioned as enclosed farmsteads for a single family or small community. The bank and fosse arrangement visible at Knockbarry is typical of the form. What makes this particular example quietly interesting is that the aerial photograph also picks up a second, fainter circular enclosure immediately to the east of it, the cropmark of another bank suggesting a closely related or contemporary structure. A third ringfort lies roughly seventy metres to the south-southeast in the same field. Finding three such enclosures in such close proximity points to a stretch of land that was, at some point in the early medieval centuries, repeatedly chosen for settlement, each generation or household marking out its own circular boundary in the earth.