Known as Lisnaboonsee, or in Irish Lios na bhFonsaí, it is a univallate rath, meaning it has a single enclosing bank rather than the multiple concentric rings seen at more elaborate sites. What makes it quietly puzzling is the state of its defences: the external fosse, the shallow ditch that would once have run around the outside of the bank, survives only in the western quadrant, a fragment just over a metre wide and barely twenty centimetres deep. Much of the eastern half of the enclosure has lost its bank almost entirely, surviving now only as a scarp, a steep drop of about one and a half metres from the interior down to the surrounding ground.

A rath of this kind would typically date to the early medieval period in Ireland, roughly between the fifth and twelfth centuries, when enclosed farmsteads of this type were among the most common forms of settlement across the country. This example has an internal diameter of 44.3 metres, making it a reasonably substantial enclosure. Some stones remain embedded in the faces of the bank in the northern sector, though whether these ever formed deliberate revetment walling, that is, a stone lining built to stabilise and reinforce the earthen bank, is unclear. There are three breaks in the bank, at the north-north-west, south-east, and west, but none can be identified with confidence as the original entrance. At the centre of the interior sits a large oval mound of stones, which is almost certainly a field clearance cairn, accumulated as farmers in a later period simply piled up stones gathered from the surrounding land.

The site was recorded and described by J. Cuppage in the 1986 Dingle Peninsula archaeological survey, a foundational survey of the Corca Dhuibhne region that catalogued hundreds of monuments across the peninsula. What lingers about Lisnaboonsee is the sense of a place that has been quietly absorbed into the working landscape around it, its original entrance lost, its ditch largely gone, and a cairn of later agricultural labour sitting at its heart.