What it actually represents is something far older: a ringfort, the type of enclosed farmstead that was built in considerable numbers across Ireland during the early medieval period, roughly between the fifth and twelfth centuries. This one sits quietly in pasture at Mornin, its outline still legible if you know what you are looking for, though the centuries have not been gentle with it.

The enclosure measures approximately 27.4 metres in diameter, defined by a low earthen bank interspersed with large boulders, nowhere taller than about 35 centimetres at its highest surviving point and roughly 4.2 metres wide. A ringfort's bank would originally have formed a meaningful boundary, sometimes topped with a wooden palisade, enclosing a farmstead and offering a degree of protection for people and livestock. At Mornin, that bank is heavily denuded, and notably absent is any fosse, the defensive ditch that typically runs along the outer edge of such monuments. Whether a fosse was never dug here or has simply vanished entirely is unclear. A gap roughly 2.9 metres wide on the eastern side may indicate the original entrance, though the break is poorly defined. The interior has been further altered by a field boundary running north-west to south-east, dividing the space into two unequal portions. Generations of agricultural activity have also left their mark: field-clearance debris has been piled against the outer face of the bank, heaped on top of it, and deposited within the interior itself, the accumulated by-product of farmers tidying their land without quite removing what lay beneath.