A shallow, grassed-over depression runs for about nine metres across a slightly raised, stone-strewn ridge. What looks like an unremarkable dip in the earth is in fact the collapsed roof of a souterrain, an underground stone-lined passage of the kind built throughout early medieval Ireland, typically for storage, refuge, or both. The passage did not simply vanish; it fell in on itself, leaving the outline of what once lay beneath.

A cashel is a type of stone-walled ringfort, and this one at Kilbride still contains enough of the souterrain to make its form legible. Along a two-metre stretch of the depression, the original drystone side walls survive to a height of about 0.6 metres, set just 0.65 metres apart, meaning the passage itself was narrow enough to demand a crouch. At the south-eastern end, the channel widens into a roughly circular cavity about one metre across and 0.8 metres deep, its walls lined with drystone masonry and its upper edge framed by a raised stony rim. Whether this was a small terminal chamber, perhaps for storing food or sheltering a person, is not certain, but its deliberate construction is plain. The care taken with even this modest, half-hidden end-point suggests it served a specific purpose within the life of the enclosure above it.