The ground barely rises, the banks have slumped almost level with the surrounding earth, and yet the geometry is still there if you know to look for it: a circular area some 32 metres across, wrapped in two concentric earthen banks with a fosse, or ditch, running between them.

This is a bivallate rath, a type of ringfort defined by its double enclosure rather than the more common single bank and ditch. Ringforts were the typical settlement form of early medieval Ireland, used roughly between the sixth and tenth centuries, and the presence of two banks rather than one is generally taken to indicate a site of some social importance, perhaps the homestead of a person of moderate rank within the local túath, or petty kingdom. The Ballylahiff example has an overall diameter of approximately 65 to 66 metres across its outer works. The inner bank, still measurable at around 9 metres wide at the base, rises just 1.1 metres above the interior and 1.2 metres above the fosse, which itself sits only marginally above external ground level. A slight gap of about 3 metres survives in the south-eastern portion of the inner bank, which likely marks the original entrance. These dimensions were recorded as part of the North Kerry Archaeological Survey, published in 1995 by C. Toal.

The site's condition is the thing that gives it an odd kind of significance. Much levelled and barely discernible above ground, it represents a very common fate for ringforts across Ireland: gradual erosion through centuries of agricultural use, until only careful measurement and a certain quality of low, raking light reveals that anything was ever there at all.