The roof of an underground chamber collapsed, exposing a souterrain, the kind of hand-dug underground passage or room associated with early medieval Irish settlements, typically used for cool storage, refuge, or both. This one had been sitting undisturbed, unannounced, and apparently unnoticed beneath the lawn.

The chamber is modest in scale: roughly 2.3 metres north to south, 1.3 metres east to west, and just about a metre in height, cut directly into the earth rather than lined with stone. What makes it particularly interesting, according to R.M. Cleary, is that the present point of entry appears to be the original entrance. In other words, whoever dug this chamber in the early medieval period used more or less the same opening that daylight now falls through. The collapse that brought it to attention was destructive, but it did not fundamentally alter the layout of what had survived.