The ringfort at Portnashangan is not an especially dramatic site on the ground, but that ordinariness is itself part of its interest. A ringfort, or rath, is a type of enclosed farmstead typical of early medieval Ireland, usually defined by one or more earthen banks and a surrounding ditch, known as a fosse. Here, that bank has been worn low over the centuries, and the fosse reduced to a shallow depression, yet the enclosure's roughly circular outline, measuring approximately 47 metres across at its widest, remains legible to anyone who knows what to look for.

The site appears on the 1837 Ordnance Survey Fair Plan map, already annotated simply as a 'fort' and shown as a circular earthwork with trees dotted around its perimeter. That early cartographic record is useful evidence: it confirms the monument was recognisable as a distinct feature nearly two centuries ago, even if it was already being absorbed into the agricultural landscape around it. A second ringfort lies just 155 metres to the west, which is a reminder that these sites were once a routine feature of the Irish countryside, clustered across the land in numbers that are easy to underestimate today. The higher ground to the north and east overlooks the site, suggesting it was positioned to take advantage of the slope's aspect rather than to command any particular view.

The perimeter bank has been incorporated into a field fence that curves noticeably outward at the north-east, tracing the monument's arc even while serving a purely modern agricultural purpose. That curve is one of the clearest indicators of the fort's presence for anyone passing close by. An aerial photograph taken in November 2011 showed the outline of the monument with considerable clarity, a reminder that early medieval earthworks often read better from above than from ground level, where centuries of ploughing, grazing, and boundary-making have done their slow work of erasure.