The site is a rath, the most common type of early medieval farmstead in Ireland, typically consisting of a roughly circular earthen bank enclosing a domestic area where a family and their animals would have lived. This particular example is subcircular in plan, measuring approximately 27.5 metres north to south and 26 metres east to west, modest dimensions that are fairly typical of single-family settlement sites from the period.

The bank is best preserved along the southern and south-western arc, and a band of denser vegetation curving from the south around through the west and towards the north-east may mark the line of an external fosse, the ditch that would originally have been dug to throw up the bank material. Fosse lines often leave traces in the soil long after the cut itself has silted and grassed over, and changes in vegetation are one of the more reliable indicators of where that ditch once ran. A gap roughly two metres wide at the south-west could be the original entrance, though it is not possible to say so with certainty. Quarrying has disturbed the north-eastern to south-eastern stretch of the bank considerably, which accounts for the uneven state of preservation. A separate enclosure lies approximately 270 metres to the west, suggesting this part of Gortnahorna was home to more than one phase or cluster of early settlement activity.