What makes it quietly unusual is the way its builders worked with the natural topography rather than against it, using the land's own contours as the primary means of defence.

A ringfort, or rath, is an enclosed farmstead of the early medieval period, typically bounded by one or more earthen banks and ditches and used as a residence by a farming family of some local standing. At Farranyharpy, the enclosure is roughly ovoid or subtriangular in plan, measuring approximately 27 metres from west-northwest to east-southeast and just over 21 metres across. On its northern, southern, and western sides, a steeply-sloping natural scarp does the work that an artificial bank would elsewhere perform. Only at the eastern end, where the spur narrows to a neck of ground, did the builders need to intervene directly, cutting off the approach with a low bank of earth and stone roughly 3.7 metres wide and 0.45 metres high, fronted by an external fosse, a shallow defensive ditch, between 1.6 and 2.7 metres wide. Inside the enclosure, a low raised platform measuring around 14.5 metres by 9.2 metres sits slightly to the northeast of centre, its purpose unrecorded but suggestive of a structural foundation or a deliberately levelled working area. The economy of effort here is notable: a single modest bank closes off the one vulnerable approach, while the site relies on natural elevation for everything else.