That juxtaposition, a corroding shell of twentieth-century machinery dumped inside a structure perhaps fifteen hundred years old, says something about how these monuments slip out of notice. The ringfort at Cooltomin sits on marshy ground, half-swallowed by vegetation, its outline legible from the air in ways that are simply not available to someone standing in the field beside it.

Ringforts, known in Irish as raths, were the most common form of enclosed settlement in early medieval Ireland, typically built and occupied between the sixth and tenth centuries. They generally consisted of a circular or sub-circular area enclosed by one or more earthen banks, with a ditch outside providing both drainage and a degree of defensive depth. The Cooltomin example is sub-circular in plan, measuring roughly 31 metres north to south and 27.2 metres east to west. Its earthen bank survives to an internal height of 1.25 metres and an external height of 2.4 metres, suggesting the ground level outside has changed considerably over time, as might be expected on low-lying and periodically waterlogged land. The external fosse, the drainage and enclosure ditch that runs from the west-southwest around to the northwest, is 3.2 metres wide and still reads at around 0.4 metres deep, though it has been partly interrupted by a field drain that opens into it at the southwest. The entrance, at 4.5 metres wide, faces east, which is common for ringforts of this type. The site was recorded by Denis Power and an aerial photograph was taken in March 2006 as part of the Archaeological Survey of Ireland.

Access is complicated by the state of the interior, which is largely impassable due to vegetation overgrowth; the edges can be approached, but the centre remains inaccessible without clearance work. The bank is best preserved at the west-northwest, where it retains something of its original profile. A field boundary curves around the southwest arc, which gives the modern landscape around the fort a subtly shaped quality that hints at how these monuments have quietly continued to influence land use long after their original purpose was forgotten. The aerial photograph in the ASI archive offers a better sense of the overall form than anything available at ground level, and is worth seeking out before a visit.