That detail alone sets the ringfort at Rahealy apart from the many grass-grown earthworks scattered across County Kerry. Sitting in the centre of a long, narrow arable field on a gentle southward slope, this is a univallate cahir, meaning a single-walled stone enclosure of early medieval type, its defining bank now softened under centuries of turf. The bank is still well-defined: it rises 1.4 metres above the interior floor and a full 3 metres above the ground outside, making the enclosed space feel both elevated and contained. The whole interior measures roughly 46 metres north to south and 44 metres east to west, large enough to have supported a substantial settlement.

What makes Rahealy particularly intriguing is what the 1841 to 1842 Ordnance Survey map recorded at this spot. The cartographers marked a feature labelled simply "Cave" in the north-western sector of the interior, where today a low mound, approximately 5 metres by 9 metres and less than a metre high, sits above the general floor level. The most plausible explanation is that this mound conceals the chamber of a souterrain, an underground passage or chamber built into ringforts during the early medieval period, typically used for storage or refuge. Souterrains were often stone-lined and corbelled, and their roofs, when the material above them shifts or settles over centuries, can produce exactly the kind of hollow resonance noted at the south-eastern end of the site, where a roughly rectangular stone-lined area returns that tell-tale echo underfoot. A possible entrance to the enclosure may have lain to the west, where stone lining was observed, though the western approach is not fully resolved. Together, the mound, the old map notation, and the sounding stone make a quiet but compelling case that considerably more lies beneath the surface here than is visible above it.