But the geometry gives it away. The enclosure measures roughly 25 metres north to south and 22.5 metres east to west, a near-circle of deliberate human making, and once you begin to read the ground it becomes surprisingly legible.

A rath is an Early Medieval farmstead enclosure, typically dating from roughly the fifth to the twelfth century, defined by a raised bank and a surrounding ditch. At Coolbeg, that ditch, or fosse, is still visible all the way round, as is the outer scarp, the slope on the far side of the ditch. The inner bank itself survives most clearly on the south-south-east to south-west arc; elsewhere the boundary presents as a scarp rather than a built-up bank, suggesting some levelling over the centuries of agricultural use. What may be the original entrance is a causewayed gap on the southern side, roughly 4.8 metres wide, where the fosse was left uncut or subsequently filled to allow passage in and out. Causeways like this are a recognised feature of Irish ringforts, and their alignment often has some practical logic, whether relating to livestock movement or the direction of a farm track long since gone.