The collapsed northern end has never been fully investigated, which means that whatever this souterrain, an underground stone-lined tunnel typically associated with early medieval settlement and used for storage or refuge, was ultimately built to conceal or protect remains an open question. The entrance itself is modest almost to the point of discouragement: just 75 centimetres high and 65 centimetres wide, facing east-south-east into the open air above the Inny river estuary.

The passage runs roughly nine metres in total, first heading west-north-west for about three metres before curving gently north for a further six. It averages 1.2 metres in height and one metre in width, which would have made movement inside uncomfortable but possible. Midway along its length, the passage constricts into a creepway flanked by four pairs of orthostats, large upright stones set to frame the gap, reducing the clearance to just 60 centimetres high and 50 centimetres wide. This kind of deliberate constriction is a feature found in a number of Irish souterrains and is generally understood as a defensive measure, forcing anyone entering to slow down and become vulnerable. Above and around the entrance, the remains of a collapsed circular hut of corbelled drystone construction survive on the terrace, suggesting this was once a coherent settlement site, a dwelling and its associated underground space used together. The whole structure sits on a carefully built stone-revetted platform overlooking the estuary below, which implies a degree of planning and effort that goes well beyond casual construction.