The ringfort, or rath, a type of enclosed farmstead typically dating from roughly the sixth to the twelfth century, was built here as a raised bank of earth with a fosse, an exterior ditch, running around its perimeter. At Parkgarriff, that fosse still survives to a depth of nearly a metre, and a section of the original bank remains standing to a height of 1.2 metres along a field fence running from the south-west to the north-west of the site.

The enclosure was recorded on the Ordnance Survey six-inch map of 1842 as a circular earthwork of approximately forty metres in diameter, a modest but legible impression on the pasture of a south-facing slope. By later editions of the same map series, the once-clear circular outline had been reduced to a slight curve in a field boundary running roughly north-north-west to south-south-east, the kind of kink in a fence line that a passing eye might not register as anything older than the last century. That gradual absorption into the field system is a familiar trajectory for ringforts across Ireland, where hundreds have been incorporated piecemeal into farm boundaries, their geometry surviving only in the occasional arc of a hedge or an unexpected rise in the ground. At Parkgarriff, the process went a step further, with residential development completing what agricultural reorganisation had begun.