It is easy to walk past without registering what you are looking at, which is part of what makes it quietly remarkable. The bank is only 0.7 metres high, barely knee-height in places, yet it traces a near-perfect circle roughly 27 metres across. Running around its outer edge, from the south-west to the north, a fosse, which is simply a defensive ditch dug to reinforce the enclosure, survives at around three metres wide and thirty centimetres deep. That it has endured at all, even in this reduced form, says something about the durability of simple earthmoving.

This is a rath, the Irish term for a ringfort, the most common type of early medieval settlement monument in Ireland. Thousands were built between roughly the fifth and twelfth centuries, serving as enclosed farmsteads for single families or small communities. The earthen bank and external ditch would have defined a household's space, offering some protection for people and livestock while marking out territory in a visible, deliberate way. The site at Cornfield was recorded as part of an archaeological survey of the Ballinrobe district, including the areas around Lough Mask and Lough Carra, compiled by D. Lavelle and published in 1994 by the Lough Mask and Lough Carra Tourist Development Association. No excavation findings are recorded, so what daily life looked like within this particular enclosure remains open.