The structure is a souterrain, an artificial underground chamber or series of chambers built from carefully stacked unmortared stone, a technique known as drystone construction. These features are relatively common across early medieval Ireland, typically associated with ringforts and cashels, the latter being the stone-walled enclosures that served as defended farmsteads. What makes this particular example quietly compelling is how much of it has already disappeared into the earth, and yet how much its collapsed state still manages to suggest.

A plan recorded by Knox and Redington in 1916 indicates that the souterrain originally comprised three chambers linked by two drop-hole creeps, narrow constricted passageways through which a person would have to lower themselves to move from one chamber to the next. These creeps were a deliberate design feature, slowing down any intruder while giving a defender the advantage. The surviving chamber runs roughly north-north-west to south-south-east, with access at its north-north-western end. Beyond that access point, a section of collapse stretching around four metres suggests the passage extended further in that direction than anything visible today. McCaffrey, writing in 1952, also noted the site, confirming it had already been in a largely ruinous state for some time. The cashel within which the souterrain sits is a separate monument in its own right, and the two together point to a settlement of some complexity, with underground storage or refuge built directly into the defensive enclosure.