A ringfort, sometimes called a rath, is an enclosed farmstead of early medieval Ireland, typically circular and defined by one or more earthen banks with a ditch, known as a fosse, running between them. This one at Kilmaglish is a bivallate example, meaning it has two concentric banks, which may indicate that its original occupants were of some local standing. The enclosure measures roughly 41 metres north to south and 40 metres east to west, and what remains of its defences tells two rather different stories depending on which side you approach from.

The northern arc of the inner bank is the most intact, and here the fosse between the two banks is still wide and noticeably deep, giving a genuine sense of how formidable the enclosure once appeared. Elsewhere the picture is less tidy. To the east, quarrying has levelled both banks and the fosse entirely, and taken a portion of the interior with it. To the west, there is a wide break in the inner bank and a narrower gap in the outer, connected by a disturbed and irregular causeway across the fosse; this western arrangement appears to be of recent rather than ancient origin, so it does not represent the fort's original entrance. The interior slopes gently downward towards the damaged eastern side, and in its western quadrant a low mound is still faintly visible, possibly the collapsed remains of a house that once stood within the enclosure. Roughly 150 metres to the north-north-west, a second ringfort sits on the same landscape, suggesting this ridge was a place people chose to settle and hold on to for some considerable time.