On the first edition Ordnance Survey six-inch map of 1839, and again on the revised edition produced between 1899 and 1900, the road bends sharply as it skirts the edge of a roughly circular enclosure. That bend was not accidental; it was accommodation. The road had been laid out, or had simply evolved over time, to respect the presence of a rath, the Irish term for a ringfort, a type of enclosed farmstead typically dating from the early medieval period, roughly the fifth to the twelfth centuries. Such enclosures, defined by an earthen bank and often a shallow outer ditch known as a fosse, were once the most common form of rural settlement across Ireland, numbering in the tens of thousands.

The Greatoak rath sat on a gentle north-facing slope in pasture land and measured approximately 46 metres in diameter. According to local memory, traces of a slight bank and a shallow outer fosse were still perceptible within living recollection. That memory is now all that supplements the cartographic record, because the enclosure was levelled during the 1970s. Once the monument was gone, the road no longer needed to curve around it. The acute bend was removed and the road now runs northeast to southwest directly through what was once the southern portion of the enclosure. The sequence is a common one in the Irish countryside: a feature endures for centuries, shapes the landscape around it, and then disappears within a single decade, leaving the straightened road as the only visible sign that something had been there at all.