This is a rath, a type of enclosed farmstead used throughout early medieval Ireland, typically defined by one or more earthen banks and ditches. What survives at Lisnafahy is fragmentary: a bank traces the northern arc of the circle, running from west-northwest through to east-northeast, while the rest of the enclosure survives only as a scarp, a low slope in the ground rather than a raised bank, and that scarp has been further obscured by a field wall built along its line at some later point.

The rath measures roughly 31 metres in diameter, a fairly typical size for a single-family farmstead of the early medieval period. Thousands of similar enclosures once existed across Ireland, and many have been lost entirely to cultivation, development, or the slow levelling of the land. At Lisnafahy, the northern portion of the bank remains the clearest evidence of what the site once was; the rest requires a degree of reading of the ground, noticing the subtle change in level where the old boundary still shapes the earth, even if the bank itself no longer stands.