The entrance is still visible, an almost circular mouth cut directly into the earth, measuring roughly 1.4 metres high by 1.5 metres wide, but it narrows quickly and slopes downward under the inner bank, and it is no longer accessible. A souterrain, to give it its proper name, is an underground passage or chamber associated with early medieval ringforts, typically used for storage, refuge, or both. What makes this one quietly remarkable is not the entrance but what lies beyond it: a branching, stonework-free labyrinth, dug entirely out of raw earth, extending to an unknown depth.

The souterrain sits within a bivallate rath, a ringfort encircled by two earthen banks and their corresponding ditches, at a location called Ráthanáin. The rath occupies the southern side of Mám na Gaoithe, a pass running through a low ridge at around 205 metres, positioned between the two crescents of low ground that cradle Ventry Harbour to one side and Smerwick Harbour to the other. It is a commanding position by any measure, controlling the natural corridor between two coastlines on the western tip of the peninsula. The souterrain opens from the base of the inner fosse, the ditch running inside the first bank, slightly east of south. In 1854, a man named Hitchcock made his way into the tunnel and recorded that it extended far underground and split into multiple passages, none of them lined with stone. That account, detailed in the Dingle Peninsula archaeological survey published by J. Cuppage in 1986, remains the most recent first-hand description of the interior.