The fence line curves in a way that no practical farmer would have planned, sweeping from south-west to east in a deliberate arc that traces the ghost of something much older. What looks, at first glance, like an ordinary corner of a pasture field on a gentle north-facing slope is, in fact, the surviving outline of a ringfort, a type of enclosed farmstead that was built and occupied across Ireland roughly between the early medieval period and the Viking Age, from around the fifth to the twelfth centuries.

The site at Killasseragh measures approximately 33 metres across in both directions, making it a fairly typical example of its class. A ringfort, or rath, was usually a circular area defined by an earthen bank and external ditch, enclosing the dwelling and outbuildings of a single farming family. Here, the original bank has been largely absorbed into a modern field fence, which stands about 1.4 metres on the interior side and 2.6 metres on the exterior, the difference in height hinting at the depth of the original earthwork beneath. In places, a stone wall has been laid on top of the older material. The bank has not vanished entirely; low undulations running from east to south-west mark its course across the ground, and the interior of the enclosure remains level, as it would have been when the site was in use. The condition is described as poor, which is a candid way of saying that centuries of agricultural activity have done what centuries of agricultural activity tend to do.

Visitors approaching the site should expect an unassuming stretch of ordinary Cork farmland. The most telling detail to look for is the curve of the field fence itself, which carries the plan of the original enclosure in its alignment even where the earthwork beneath it has been reduced to little more than a ripple in the grass.