On the southern slopes of the Knockmealdown Mountains, an ancient roadway lies half-buried in the hillside, visible in places as a sunken track roughly three metres wide and sunk up to a metre into the ground, and in others simply as a stream-bed following the old line of travel. This is the Rian Bó Phadraig, the Road of Patrick's Cow, a name that gestures at the deep antiquity the route was credited with long before anyone tried to measure or map it.

The road is traditionally understood to have connected Cashel, seat of the kings of Munster, with Lismore, whose monastery founded by St Carthage became one of early medieval Ireland's great centres of learning. Charles Smith, writing in his 1746 history of County Waterford, described it as a double-ditch construction believed to extend all the way from Cashel to Ardmore by way of Lismore. By 1773, Scalé's maps were recording it more prosaically as the road from Lismore to Ardfinnan, suggesting it remained a functioning or at least recognised route well into the early modern period. The course within County Waterford was traced in detail by Rev. P. Power, whose 1905 paper in the Journal of the Royal Society of Antiquaries of Ireland established that, on the Waterford side of the mountains, the road ran in a remarkably straight line from a pass at the summit of the Knockmealdowns down to St Carthage's monastery at Lismore.

The only surviving section in County Waterford runs for approximately three kilometres, from the Clongeen to Cappoquin road at the mountain foothills, through the townlands of Reanabarna and Knockannanagh, up to the summit pass, where it crosses into County Tipperary and continues on the far side. Walking the route, the sunken hollow of the old way becomes clearest where it cuts through open ground; a medieval sunken road, worn down by centuries of foot, hoof, and wheel traffic, is exactly what it resembles. An older townland boundary appears to overlie part of the track, a detail that quietly suggests the road had already fallen out of primary use by the time the boundary was fixed.