At Ballyhoreen in County Westmeath, however, that is precisely what happened. An earthen ringfort, a roughly circular enclosure of the kind built across Ireland from the early medieval period onwards as a farmstead defended by a bank and ditch, sits on a low natural rise in wet grassland, and at some point the demands of industrial water management cut straight through its western side.

The 1837 Ordnance Survey six-inch map still shows the ringfort as a circular enclosure, already intersected at the west by the mill race serving a corn mill some 520 metres to the north-north-west. By the time the revised twenty-five-inch map was produced in 1911, the feature had disappeared from the cartographic record entirely, suggesting that whatever remained above ground had become too degraded or too absorbed into the agricultural and industrial landscape to merit marking. What survives today is a sub-circular area roughly 40 metres north to south and 45 metres east to west. The enclosing earthen bank is poorly preserved and only legible at the south-west. The interior itself is slightly unusual in its topography: the ground rises from the perimeter inward, levelling off at the centre into a shallow depression, a profile that can indicate an infilled or subsided interior feature. The mill race running north-north-east to south-south-west still intersects the monument from the west and south-west, a reminder that the site's slow erosion was not simply the work of ploughing or neglect but of deliberate industrial engineering. A second ringfort lies just 105 metres to the north-east, making this a corner of Westmeath that once held a notable concentration of early medieval settlement, now largely swallowed by damp pasture.