What makes it worth pausing over is the sheer bulk of what has survived. The inner bank, though barely visible from the inside, rises to a formidable 6.2 metres on its outer face, while a second outer bank and an intervening fosse, a defensive ditch dug between the two ramparts, complete a defensive arrangement that speaks to a level of effort and status well beyond the ordinary farmstead.

This is a rath, the Irish term for a ringfort, a type of enclosed circular settlement built predominantly between the sixth and tenth centuries, typically by farming families of some local standing. Most raths consist of a single bank and ditch, so the presence of two concentric banks here, separated by a fosse some 2.5 metres wide, places this example in a more substantial category. The outer bank reaches 2.4 metres in height and shows evidence of internal stone facing along its south-south-west to south-west arc, suggesting deliberate construction rather than simple earth-piling. Along the northern arc it becomes flat-topped and widens to 2.4 metres, possibly indicating later modification or a differing construction phase. A causeway entrance cuts through both banks at the east-north-east, measuring 4.6 metres through the inner bank and 7.4 metres through the outer, wide enough to have admitted animals as well as people. The fosse itself is littered with loose stone and flattens at the south-west. A remnant of dry-stone field wall abuts the outer bank at the south-east, a later agricultural addition that hints at how the landscape around the rath has continued to be worked across the centuries. The site was recorded and compiled by Denis Power.

Knockfierna Hill carries its own layer of folklore and mythology in the wider Limerick landscape, and the rath sits on its south-facing slope within what is now rough grazing land. The interior is level and under pasture, with no visible surface features within the enclosed area. Visitors approaching on foot should expect uneven ground, particularly around the fosse where loose stone collects. The banks are clearest when light falls at a low angle, in early morning or late afternoon, which allows the changes in height and the subtle transition between preservation states to become more readable. The best-preserved stretch of the inner bank runs from the west-south-west around to the north-east, and that arc is the most rewarding to walk.