It is easy to overlook, which is partly what makes it worth a second look. The enclosure is roughly circular and levelled, the kind of feature that might be dismissed as a natural irregularity in the field until you begin to trace its edges and notice how deliberately it sits in the landscape.

A rath is an early medieval enclosure, typically dating from roughly the fifth to the twelfth century, formed by one or more banks of earth and an accompanying fosse, or ditch, dug to provide the material for the bank. They served as farmsteads and settlement enclosures, and tens of thousands survive across Ireland in varying states of preservation. The Clashnevin example measures approximately 34 metres north to south and 37.6 metres east to west, making it a modest but not unusually small example. When the Office of Public Works recorded it in the 1950s, the bank still stood to an external height of about 0.6 metres, with the enclosing fosse reaching roughly 1.8 metres in width and 0.3 metres in depth. Traces of the fosse survive most clearly on the eastern side. The northeast quadrant presents a slightly different picture, where a field fence was cut across the enclosure at some point, interrupting the circuit. That small intrusion is itself a quiet record of the centuries between the rath's construction and the present day, when field boundaries were drawn without much concern for what lay beneath.