That piece of folklore, recorded by Ua Riain in 1927, is the most vivid detail attached to this ringfort on the north-sloping hillside above Coars, and it points to the feature that sets this particular site apart: a souterrain, an underground stone-lined passage or chamber system built in early medieval Ireland, typically for storage or refuge, that has since collapsed into two rectangular depressions in the northwest corner of the enclosure.

The rath itself is bivallate, meaning it has two concentric earthen banks rather than the single bank more commonly encountered. The inner bank, still averaging 2.3 metres above the base of its fosse, retains short stretches of drystone revetment on its inner face, the stonework helping to hold the earthwork in shape. Between the two banks runs a flat-bottomed fosse, a defensive ditch now heavily silted and in places waterlogged, roughly three metres wide. The outer bank is lower and less substantial. The probable original entrance faces east, where a two-metre gap through the inner bank is flanked by drystone walling on its north side, and the corresponding gap through the outer bank splays outward from 2.2 metres to 4.5 metres, a widening funnel shape that would have made the approach manageable for people and animals. The whole enclosure, roughly 30 metres across, is densely overgrown, which is typical of sites like this across Kerry but also means that the structural detail described by A. O'Sullivan and J. Sheehan in their 1996 archaeological survey of the peninsula requires some effort to read in the vegetation.

The souterrain is now fully collapsed, its former passage indicated only by those two sunken rectangular areas, up to 0.7 metres deep, with traces of slightly corbelled stonework, where flat slabs are stacked in overlapping courses to form a rough arch, visible in the sides of one depression. Whether the boys of 1927 were exploring a still-intact section or simply following a rubble-filled void is impossible to say now, but eight rooms suggests a notably complex structure for what is, in other respects, a moderately sized enclosed settlement site.