Whether the name refers to the colour of the soil, the vegetation that once darkened it, or something less tangible is now lost, but it attaches a character to the earthworks that bare measurements cannot quite convey. Sitting on rising ground in north Kerry with open views across the surrounding countryside, this is not a site that hides itself.

What makes Lisduff structurally notable is that it is bivallate, meaning it is enclosed not by one bank and ditch but by two concentric rings of earthwork. Most ringforts, the circular enclosed farmsteads built in their thousands across Ireland during the early medieval period, roughly the fifth to twelfth centuries, make do with a single bank and fosse. The double circuit here is more substantial than average. The inner bank runs to about 6.3 metres wide at the base and stands up to 2.7 metres above the steep, U-shaped ditch inside it. The outer bank is wider still, at 7 metres across the base, and rises to 3.4 metres above the outer fosse. The interior measures roughly 31 metres north to south and 34 metres east to west, a generous enclosure by any standard. A track cuts through the outer fosse to the south-west and west, which is the main visible disturbance to an otherwise well-preserved monument. The site has been under a preservation order since 1976, a recognition of how intact the earthworks remain.