The result is an unusual collision of ancient and everyday: an oval enclosure that once stood complete on its low rise in County Limerick now has a functioning public road running through its northern edge, the tarmac set into a deep trench that effectively amputates part of the site's history.

A ringfort, or rath, is an enclosed farmstead of the early medieval period, typically circular or oval and defined by one or more earthen banks and ditches. This example at Glenwilliam sits on a north-facing slope, and its roughly oval interior measures about 28 metres north to south and 22 metres east to west. The enclosing bank still survives across much of its circuit, rising around 0.9 metres on the interior face and 1.3 metres externally, with an accompanying fosse, or ditch, running four metres wide and 1.2 metres deep. On the north-east to south-east arc, where the natural ground falls away sharply from the hillock, the bank takes on more of a scarp character, using the terrain itself as part of the defensive or enclosing logic, reaching an effective height of around five metres over a spread of 24 metres. The road has truncated the north-west to north-east section of the enclosure, and an earthen bank surviving on the road's north side appears to arc slightly outward in a way that may echo the original line of the enclosure, though it is more likely part of the surrounding field boundary system. Stone dumps at the south-east have further obscured what remains there. The site was compiled and recorded by Denis Power, with details uploaded in August 2011.

The interior is level ground under pasture, so there is nothing dramatically visible once inside the circuit. The most striking element is the road cut itself, visible as you approach, where the hillside has been sliced open to reveal the scale of what the hillock actually amounts to. The south-east portion of the enclosing element is the most obscured, buried under field clearance stone, while the north-west arc is simply gone, replaced by tarmac. Visitors who know what they are looking at will find the surviving bank and fosse most legible on the north and west sides, before the road interrupts the sequence.