By 1972, there was nothing left to see. A rath that had given its name to the place, that appeared on maps for over seventy years, and that once measured roughly 75 metres across had vanished entirely into the tillage of a low ridge in County Kildare.

A rath is a ringfort, a circular enclosure defined by an earthen bank and ditch, typically dating from the early medieval period and associated with farming settlements and high-status residences. Rathglass was a substantial example, large enough to be conspicuous on the first edition of the Ordnance Survey six-inch map of 1839, where it appears as a clearly defined circular enclosure with a surrounding bank, named explicitly on the sheet. It was not alone: two further raths lie to the south, forming a cluster of three on the same low east-west ridge, suggesting the area was a focus of early medieval activity. By the time the revised edition of the map was produced in 1910, something had already gone wrong. Only the western half of the monument was still being depicted, and that remnant was shown to contain a quarry pit. The stone or gravel extracted there had, in all likelihood, been eating into the earthwork for decades. Between the quarrying and the steady pressure of agricultural cultivation on the surrounding tillage land, the rath was progressively levelled until, by the early 1970s, no surface trace remained at all.

What survives today is essentially a placename and a cartographic record. The ridge itself is still there, and the two associated raths to the south may preserve more of their original form, but Rathglass proper exists now only in the sequence of maps that tracked its slow disappearance.