That absence is itself a kind of document. A ringfort, or rath, once stood here: a roughly circular earthen enclosure, the sort of defended farmstead that tens of thousands of Irish farming families occupied during the early medieval period, roughly from the fifth to the twelfth centuries. This one measured approximately thirty metres in diameter, a modest but entirely typical size, and its circular outline was clear enough to be recorded on the Ordnance Survey's six-inch map of 1842, marked with the hachured lines surveyors used to indicate a raised bank.

What the later maps show is a process of slow erasure. By 1905, and again on the 1935 revision, the eastern face of the surrounding bank had been straightened into a flat line, with right angles formed at the northeast and southeast corners. The curving prehistoric boundary had been squared off to suit the geometry of agricultural use, the ancient enclosure gradually absorbed into the practical logic of a working farm. At some point after that, the levelling was completed entirely. Machinery cut up the ground surface so thoroughly that no visible trace now remains above ground. The rath at Carrigdownane did not survive dramatically, through collapse or flood or fire; it was simply made inconvenient, and then made to disappear.