When archaeologists opened the ground at Earlsrath in 2006 ahead of the N9/N10 Waterford to Kilcullen Road Scheme, they found a curving boundary ditch slicing clean through the remains of two Early Neolithic houses. That relationship between the ditch and the houses beneath it tells a quiet but striking story: whoever dug the boundary had no idea, and no reason to care, that people had built and lived on that same ground roughly five thousand years before.

The ditch itself is substantial. Running at least 31.5 metres within the excavated area, between 1.5 and 2.25 metres wide and around a metre deep, it was cut with a V-shaped profile, the kind of sharp-sided form typically associated with boundary or drainage work rather than defensive ditching. Radiocarbon dating placed its construction somewhere between cal AD 689 and 965, which puts it firmly in the early medieval period, the centuries when Ireland's landscape was being parcelled into the kind of territorial and agricultural units recognisable in later townland boundaries. The full extent of the feature remains unknown. Test trenches dug to the south-east showed it continuing for approximately 70 metres further in that direction, suggesting a boundary of some scale, though where it begins or ends has not been established. Underneath it, the two Neolithic houses it disturbs belong to a phase of settled farming activity from around 3800 to 3600 BC, a period when the first generations of agricultural communities were clearing woodland and constructing timber or post-built rectangular structures across Ireland. The ditch's builders left no sign of knowing any of this, but the stratigraphy recorded it faithfully.