The fosse, as it is properly called, is one of the defining features of these early medieval enclosures, the circular earthworks that once served as farmsteads and homesteads across Ireland, perhaps from the fifth century onwards into the Norman period. The rath at Killegar in County Wicklow is quietly anomalous in this respect: no fosse survives, and no trace of internal features remains either, leaving a circular enclosure that presents itself almost as a bare outline of its former self.

What does survive is legible enough on the ground. The enclosure measures roughly 25 metres in diameter, defined around most of its circuit by an earth and stone bank about three metres wide and standing no more than 0.4 metres above the surrounding ground. On the northern, upslope side, where the terrain rises against the enclosure, a steeper scarp takes over from the bank, reaching about 0.7 metres in height and reinforced by a low revetment of stone, a practical response to the pressure of the hillside bearing down from above. The whole sits on a gentle south-facing slope, an orientation that would have made good sense to whoever chose the spot, catching light and draining water away from the enclosed area. A possible entrance, just 1.6 metres wide, appears at the northeast, though the evidence is tentative.

The site is modest in scale and unspectacular in condition, which is part of what makes it worth attention. Thousands of ringforts survive across Ireland in varying states of preservation, and Killegar represents the quieter end of that spectrum: no dramatic banks, no obvious internal archaeology visible at the surface, just the faint geometry of an early medieval life pressed into a Wicklow hillside.