The enclosure itself, roughly 35 metres across at its widest, is bisected by a disused field wall and reduced in most places to little more than a low scarp or a scrappy earth-and-stone bank. Heaps of cleared stone confuse the south-eastern interior, and casual visitors might dismiss the whole thing as an unremarkable smudge in the landscape. Beneath it, however, runs the most extensive souterrain recorded on the Dingle Peninsula: a 33-metre-long underground complex of eight chambers connected by narrow, often vertiginous passages, most of them tunnelled directly out of the bedrock. A souterrain, in the Irish archaeological context, is an artificially constructed underground passage or chamber, typically associated with Early Medieval ringforts and used variously for storage, refuge, or concealment. This one is in a different league from the typical example. When stones were being quarried from the site by the current landowner's father, a slab-lined grave was uncovered, and inside it an iron box containing coins.

The souterrain begins with two drystone-built corbelled chambers connected by a low creepway, the entrance gap a mere 63 centimetres wide and 37 centimetres high. From there the structure drops away into rock-cut territory: L-shaped tunnels, irregular chambers up to five metres long, and passages that narrow to 35 centimetres at their tightest point. Passage six, the most demanding stretch, is only 55 centimetres high at its mid-point. The fifth chamber is currently a dead end, though whether it was always so remains unresolved. Researchers have proposed that the enormous volume of spoil generated during construction was not hauled back through the entrance but removed via pits sunk from the surface, which were later backfilled and are now invisible above ground. Two such pits are thought to lie between chambers three, four, and five, and between chambers six, seven, and eight. Deane, writing in 1893, noted a skull and other bones in chambers four and seven. Champneys, in 1910, appears to have been describing the same remains when he referred to two bodies found in a sitting position in a very elaborate souterrain near Ventry. Deane also recorded the foundation of a hut overlying the souterrain entrance, suggesting that the underground works and the surface settlement were in use simultaneously at some point.