It is easy to walk past without registering what you are looking at, because the earthen bank is only a few centimetres high and the surrounding ditch barely a hand's depth below the field level. Yet the geometry is precise enough, and the proportions deliberate enough, that once you see it as a whole, it becomes unmistakable as human intention rather than a natural feature of the land.

The site at Ardnacrohy is a rath, the most common type of early medieval enclosure in Ireland. A rath is essentially a ringfort defined by earthen rather than stone construction, typically built between roughly the fifth and tenth centuries and used as a farmstead or small settlement by a single family or household. This example measures approximately 29 metres north to south and 27 metres east to west, enclosed by an earthen bank with a complementary external fosse, which is the shallow ditch running around the outside of the bank. The dimensions here are modest; the interior bank stands only about 25 centimetres above the interior ground level, and the fosse is roughly 20 centimetres deep and 2.3 metres wide. These are not defensive works in any dramatic military sense, but rather boundary markers, enclosures for livestock, and a statement of ownership and social standing in an early Irish farming landscape. The record was compiled by Denis Power and uploaded in August 2011.

The enclosure sits at the base of a slight north-west-facing slope, which gives the surrounding land a gentle tilt that helps orientate you once you are on the ground. The interior is described as level, dry, and clear of overgrowth, which is relatively unusual for a site of this age and means the circular outline should be reasonably legible even from within the enclosure rather than just from above. One whitethorn bush grows on the bank at the west-north-west point, a detail worth looking for both as a navigational marker and as a small piece of living folklore; lone hawthorns on ancient earthworks are frequently left uncut out of long-held local custom, their presence on fairy mounds and old raths considered unlucky to disturb.