A rath, in Irish usage, is a roughly circular or oval earthen enclosure, typically of early medieval date, formed by a raised bank and sometimes an outer ditch. The one at Courtnaboghilla was considerably larger than most, measuring approximately 95 metres on its northeast to southwest axis and around 60 metres across, and it was divided internally by a straight boundary running northwest to southeast, an unusual feature that sets it apart from the common single-ringed form. By the time anyone thought to investigate it properly, it had already largely disappeared.

The enclosure appears clearly on the first edition Ordnance Survey six-inch map of 1839, marked with the hachured lines surveyors used to indicate earthworks, which means it was still a visible feature of the landscape at that point. The southeast portion of the bank had, at some stage, been reduced to little more than a cropmark, the kind of faint discolouration in growing crops that reveals a buried fosse, or ditch, below ground level. Then in 1958, during bulldozing work to level the site, human skeletal remains were uncovered at a depth of between 0.3 and 0.6 metres. Most of the bone was disturbed by the machinery, but some individuals were found lying in a supine position, oriented east to west, a burial alignment commonly associated with Christian practice. The discovery is recorded by Cahill and Sikora in their 2011 study, though the circumstances meant that relatively little could be recovered or properly analysed. Aerial photography confirmed what the map had suggested, and satellite imagery as recent as July 2018 still shows traces of the enclosure's outline from above, even where nothing is visible on the ground.