The bank is heavily overgrown now, but it still reads clearly as an enclosure, rising to an internal height of around 1.6 metres and spanning some 34 metres from north to south. What gives it an immediate human quality is the entrance gap to the south-south-east, nearly 7.6 metres wide, wide enough to have admitted livestock, people, and perhaps a cart. A second, narrower gap of around 4 metres opens to the north.

This is a rath, the most common type of monument in the Irish countryside. Raths are enclosed farmsteads of the early medieval period, roughly the fifth to twelfth centuries, built by farming families who used the earthen bank and its accompanying external fosse, or ditch, as a boundary marking status and providing a degree of security for animals. At Knocknabehy, the fosse has softened considerably over the centuries and now reads only as a gentle slope inward to the base of the bank, the kind of subtle topographic detail that is easy to miss unless you are looking for it. A field fence cuts across the site from east to west, a reminder that working farmland has never stopped pressing against these older boundaries.