The cashel at Barnalyra occupies a low rise in pasture land in Co. Mayo, its outline still legible as a roughly circular spread of grass-covered stone, measuring about 33 metres north to south and just under 30 metres east to west. A cashel is a type of ringfort defined by a stone rather than earthen boundary wall, and here that wall survives as a broad, low bank rather than anything upstanding. At its most intact, along the eastern and southern arc, it runs five to six metres wide and rises about a metre on the outer face, where a later property boundary happened to skirt the edge and offered the old structure some incidental protection. Elsewhere the bank is irregular and worn.

The most telling detail is a narrower, lower section in the north-east of the circuit, roughly four metres wide, which probably marks where the original entrance once stood. Inside, the ground is level and grassy, unremarkable to the eye but not entirely empty: in the south-western quadrant there is a souterrain, an underground stone-lined passage or chamber of the kind commonly associated with early medieval settlement in Ireland, sometimes used for storage, sometimes for refuge. Just beyond the cashel to the north, a low linear rise runs east to west across the ground; it has the character of an old field boundary rather than any outer defensive work associated with the cashel itself. The enclosure, in other words, is what it appears to be: a single-phase stone ringfort, sitting quietly in a working landscape, with a buried chamber beneath its floor and two twenty-first century houses for neighbours.