The first six-inch map of 1837 shows nothing at this location. Only by the revised twenty-five-inch map of 1913 does the enclosure appear, marked as an earthwork, its outline already compromised by the field boundaries that had grown around and through it. The fact that it escaped the attention of the nineteenth-century surveyors entirely is itself curious, though it may simply reflect how thoroughly the surrounding landscape had, by that point, absorbed the monument into its working agricultural fabric.

A rath is the Irish term for a roughly circular or oval ringfort, typically formed by a raised earthen bank enclosing a central area, and used from the early medieval period onward as a farmstead or settlement. At Tonlemony, the enclosure measures approximately 38 metres north to south and 34 metres east to west. When fieldwork was carried out in 1980, the bank was still traceable around most of the perimeter, though in varying states of preservation: reduced to a scarp along the south-western through to north-north-eastern arc, levelled almost entirely along the north-north-eastern to south-eastern stretch, and folded into a field fence along the southern side. Where the bank has been levelled, the perimeter can still be detected as a faint rise in the ground. There is no visible entrance gap and no sign of an external fosse, the ditch that typically accompanies a bank of this kind. Inside the enclosure, the ground rises gently toward the centre, and small outcrops of rock break through the surface in the western and south-eastern quadrants. Running east to west across the interior, and even extending over the levelled eastern edge, are faint traces of old cultivation ridges, suggesting the interior was at some point ploughed or spaded, long after whatever original use the ringfort served had ended. The ridge on which it sits commands extensive views across the undulating pasture in all directions, a position consistent with the practical logic of early medieval settlement, where elevation offered both surveillance and drainage.