This is the kind of monument that rewards a careful eye rather than a first glance: a raised platform roughly 26.8 metres in diameter, ringed by a bank of earth and stone and surrounded by a shallow external fosse, the term for the ditch that typically runs around the outside of such an enclosure.

The site belongs to the broad category of ring forts, known in Irish as raths or lios, which were among the most common forms of rural settlement and enclosure in early medieval Ireland, used variously as farmsteads, enclosures for livestock, or places of local significance. At Lisnacush, the bank reaches a maximum height of just 0.65 metres and a width of 3.4 metres, while the fosse beyond it is 5.1 metres wide but only 0.2 metres deep, shallow enough that it would barely register underfoot if you were not looking for it. A field boundary running roughly north-north-east to south-south-east skirts the fosse along its northern and eastern arc, suggesting that later agricultural organisation has wrapped itself around the older monument without entirely erasing it. Large boulders have been folded into the fabric of the bank, possibly gathered during field clearance at some point and added to what was already there. Both the bank and the fosse have been considerably worn down by cattle moving across the site over many generations, and no trace of an original entrance survives in a recognisable form.