The structure is a cashel, the Irish term for a ringfort built from dry stone rather than earthen banks, and despite the overgrowth, enough survives to read the shape of it clearly: a rough circle roughly fifteen and a half metres across, with a wall that at its widest measures over five metres at the base.

Cashels like this one were typically built during the early medieval period, roughly between the fifth and twelfth centuries, and served as enclosed farmsteads for a single family or small household. The drystone construction, laid without mortar, was a practical response to a landscape where stone was plentiful and timber was not always easy to come by. At Lisheenacrannagh, the wall still stands to an internal height of just over half a metre in places, though the external face has been worn down further, to around thirty centimetres. That the structure survives at all, even in this obscured state, is largely down to the fact that farmland tends to absorb rather than demolish such things, the stones slipping gradually under soil and scrub rather than being carted away for building elsewhere.