A souterrain is an underground stone-lined passage or chamber, typically associated with early medieval ringforts and used for storage, refuge, or both. This one was filled in around 1919, and today there is no surface trace to indicate it ever existed.

The site was recorded by Hartnett in 1939, by which point the souterrain had already been gone for roughly two decades. His account places the original opening inside the rampart to the north-east of the ringfort. He was also told locally of a second opening inside the rampart to the south-west, suggesting the structure may have had more than one entry point, which was not unusual for souterrains of this type. A further possible souterrain has been noted outside the outer bank of the ringfort entirely, a separate feature that adds another layer of uncertainty to what lies underfoot here.

For a visitor, there is genuinely nothing to see at the souterrain itself. The interest lies in what is absent: a deliberate infilling, local memory of a second entrance passed on to a researcher, and the quiet possibility that more than one underground feature survives unexamined beneath the surrounding ground.