Measuring roughly 27.8 metres in diameter, the raised enclosure is easy to overlook precisely because time has been so thorough in softening it. What was once a deliberately constructed boundary, clear enough to mark out territory or enclose a settlement, now reads as a subtle swell in the ground, the kind of thing that rewards a careful eye rather than a casual glance.

Circular enclosures of this type are a recurring feature of the Irish landscape, and their purposes varied considerably. Some functioned as ringforts, the enclosed farmsteads of early medieval Ireland where a family and their livestock sheltered within an earthen bank and ditch. Others may have served ceremonial or boundary functions that are now harder to read. At Knocknagappagh the enclosure's exact character is uncertain, its defining features too eroded to say with confidence what it once was. What sharpens the interest somewhat is the proximity of a ringfort, a better-preserved example of the classic earthwork farmstead type, sitting around 200 metres to the north-east. Whether the two were ever connected in function or period is unknown, but their closeness on the same slope suggests this quiet corner of north Galway was once a good deal more occupied than it appears today.