It is a quietly odd detail, a modern boundary line unconsciously echoing a boundary that is well over a thousand years old, and it says something about how thoroughly these early medieval enclosures have been absorbed into the working landscape of rural Ireland.

A ringfort, or rath, was typically the enclosed homestead of a farming family during the early medieval period, roughly the fifth to the twelfth centuries. The one at Lissard More sits prominently on a northwest to southwest ridge in County Mayo, taking full advantage of the ridge's natural topography. The builders here did not simply impose a circular bank on flat ground; they incorporated the steep southern slope of the ridge into the design, letting the natural fall of the land do some of the defensive work. The result is a raised oval platform measuring approximately 35 metres on its northeast to southwest axis and 24 metres across. It is defined by a substantial earthen scarp, nearly two metres high in places, and enclosed by a fosse, which is the technical term for the ditch dug around such an enclosure. That fosse survives in varying states of legibility: clearly visible as a shallow depression to the north and east, reduced to a barely discernible trace on the southeast and south, and apparent on the west and north as a terrace with a pronounced outer scarp. An arc of external bank, widening to nearly five metres, survives at the northeast. A large boulder sits at the base of the western scarp, and the southern half of the perimeter is thickly overgrown. Lough Brohly lies visible to the northeast, and a small river draining from the lough runs roughly 130 metres to the southeast at the base of the ridge. A derelict farmstead stands about 50 metres to the south, a reminder that this land has been continuously worked across very different eras.