A rath is a ringfort, the kind of enclosed farmstead that was the standard unit of rural settlement in early medieval Ireland, and this one at Fanore Beg is defined by a combined stone and earthen bank roughly five metres wide and standing between one and one and a half metres high, with an outer ditch, or fosse, running around it. The bank and fosse are best preserved on the western and northern sides; elsewhere the bank has been reduced to a low scarp, and the fosse disappears entirely between the north and south-east arc. Two possible causeways cross the fosse on the south-west and north-west sides, suggesting where entrances once were.

The site was already considered significant enough to be marked by hachuring on the Ordnance Survey six-inch maps of both 1842 and 1915, meaning surveyors in successive generations recognised the earthwork as something worth indicating. The interior holds a later intrusion: a wall of roughly dressed stone and mortar running west-north-west to east-south-east cuts across it, a reminder that these enclosures were frequently reused or altered long after their original construction. An overgrown bank of ancient appearance also meets the site at the east-south-east. Most intriguingly, the rath sits at the western edge of a multiperiod field system covering approximately eight square kilometres, a landscape of boundaries and enclosures representing activity across several different periods. The rath is, in that sense, one legible point within a much larger and longer-running pattern of human organisation of the land.