At Pollbrean, the outline of a circular enclosure roughly forty metres in external diameter shows up as a vegetation mark on aerial photographs, the kind of subtle colour variation in crops or grass that betrays buried ditches long after any visible earthwork has been levelled or ploughed away.

What the photographs capture is the ghostly signature of a rath, the Irish term for a ringfort enclosed by an earthen bank and one or more surrounding ditches. At Pollbrean, the enclosure appears to have been defined by two fosse features, a wide inner ditch and a narrower outer one, a double-ditch arrangement that would have given the site added enclosure and perhaps added status in its day. The fort sits on a slight north-to-south ridge, an almost imperceptible rise in an otherwise flat landscape, the kind of marginal topographic advantage that early medieval farming communities in Ireland often sought when choosing where to build. Ringforts of this type were typically domestic enclosures, the enclosed farmsteads of landowning families during the first millennium, though their earthworks were also used to pen livestock and mark social boundaries. At Pollbrean, the surface features have either been lost or reduced to the point where only the differential growth of plants over disturbed subsoil still traces the original plan.