What makes it quietly anomalous is the sheer preservation of that bank, which rises more steeply and prominently than it might otherwise appear because someone, at some point, quarried into the northern interior, scooping out over a metre of depth and so exaggerating the visual drama of the enclosing wall from within.

This is a rath, the more technical term for a type of ringfort built from earth rather than stone. Ringforts, constructed mainly during the early medieval period, roughly the fifth to the twelfth centuries, were the homesteads of farming families, enclosed by a bank and, originally, a fosse, the external ditch that ran around the outside to reinforce the boundary. At Garryroan, that outer fosse has since been filled in, leaving only the raised bank itself to define the circle. The surviving structure measures 34.3 metres across on its north to south axis, though the east to west measurement could not be properly recorded, the western quadrant being too heavily choked with bramble to allow access. The entrance, just two metres wide, is cut into the southern part of the bank, where the earthwork gradually reduces in scale as it approaches the gap, a typical arrangement designed to funnel movement through a single controlled point.