The name references a lios, or ringfort, yet no visible trace of one remains above ground. What does survive, just about, is a souterrain: an underground stone-lined passage system of the kind built throughout early medieval Ireland, typically associated with ringfort settlements and used for storage or refuge. This one has been collapsing slowly for decades, and it is partly through those collapses that it has been examined at all.

The structure was first investigated in 1930, when excavators recovered a fragment of a rotary quern, a hand-operated stone used for grinding grain, now held by the National Museum of Ireland. The site was revisited in May 1991 following further collapse, and the layout that was recorded then consists of three earth-cut chambers connected by creepways, the low narrow passages that link one chamber to the next and would have required a person to crawl between them. The first chamber, irregular in shape and only about 55 centimetres high along its long axis, retains its original entrance: a stone lintel supported on one side by an orthostat, a single upright stone, and on the other by dry stone walling. From there, the chambers grow progressively larger. The second is roughly oval, just over a metre high, and the third, also oval, reaches 1.2 metres in height and four metres in length, though its southern end has seen recent collapse. Each chamber also has a construction shaft, the vertical opening used during building to excavate and remove material; one is blocked, another obscured by fallen stone. That the quern fragment survived here at all suggests domestic activity close by, even if the ringfort that almost certainly accompanied this souterrain has left nothing visible on the surface.