A souterrain is an underground stone-lined passage or chamber, typically associated with early medieval ringforts and used variously for storage, refuge, or ventilation of dwellings above. The word is reputedly the operative one here: the passage's precise location within the fort has not been confirmed by excavation, and the ground around it has been substantially disturbed by tree roots and the accumulated dumping of field clearance over generations. What remains visible at the surface is ambiguous, partial, and quietly compelling.

The fort itself, known locally as An Lios Garbh or Lisgarve, is a bivallate rath, meaning it was originally enclosed by two concentric earthen banks rather than one. It occupies an elevated position on the valley slopes, looking out across the Milltown river and over Dingle Harbour towards the Iveragh Peninsula. The interior retains a scatter of low mounds in its northern sector, along with short stretches of drystone masonry on the inner face of the bank. One section, roughly circular in plan and abutting the bank at the north, survives to a height of 0.7 metres and is slightly corbelled, a construction technique in which stones are laid so that each course projects inward beyond the one below. Whether these features relate to the souterrain itself, or to earlier surface structures of some other kind, could not be determined when the site was surveyed by J. Cuppage for the Dingle Peninsula archaeological survey published in 1986. The ruins were already too fragmentary for confident classification.