A rath, sometimes called a ringfort, is essentially a circular area enclosed by one or more earthen banks and ditches, constructed during the early medieval period, roughly between 500 and 1200 AD. They served as farmsteads and family enclosures, the everyday living spaces of rural Ireland for centuries, and Callanafersy preserves one such example within its boundaries.

Ringforts are Ireland's most numerous archaeological monument type, with estimates suggesting somewhere in the region of 40,000 to 50,000 once existed across the island. Kerry, with its relatively undisturbed rural terrain, holds a notable concentration of them. The townland name Callanafersy itself sits near the Caragh River estuary on the Iveragh Peninsula, a part of Kerry where early medieval settlement left considerable traces in the ground. These enclosures were not defensive structures in any military sense, despite their bank-and-ditch construction; the earthworks more likely served to define territory, contain livestock, and signal the social standing of the family within. Some raths were later folded into local folklore as the dwelling places of the sídhe, the supernatural inhabitants of the otherworld in Irish tradition, which helped preserve many of them from destruction by cautious farmers across the centuries.