What makes it worth a second look is the detail in its construction: the outer face of the bank is stone-faced, suggesting that whoever built it wanted something more durable than a simple mound of piled earth, and the external fosse, a defensive ditch cut around the outside of the bank, survives on the north-north-west to north-west side, though it has since been filled in.

This is a rath, the most common type of ringfort found across Ireland, typically dating from the early medieval period, roughly the fifth to the twelfth centuries. Ringforts served as enclosed farmsteads, with the bank and ditch providing security for a family, their livestock, and their stores rather than functioning as a military fortification in any grand sense. The Knocknageehy example measures 34 metres in diameter, a fairly typical size, with the internal height of the bank reaching up to 1.8 metres at its tallest point. One section on the north-north-west side, about 2 metres long, is level with the interior, which likely marks the original entrance gap. The stone facing on the exterior of the bank is a notable feature; many earthen ringforts show no such facing, and its presence here points to some deliberate effort to reinforce or ornament the structure's outer profile.