Somewhere within the earthworks of a rath, the circular bank-and-ditch enclosure that was a common feature of early medieval farming settlement in Ireland, a cavern was noted by surveyors in the 1840s, its entrance already blocked up by the time they passed through. Today there are no visible remains of what may have been a souterrain beneath it.

A souterrain is an underground passage or chamber, typically stone-lined, built in association with early medieval raths and ringforts. They served various purposes: cool storage, refuge, or escape routes. The one at Leamnaguila, if that is indeed what the cavern was, belonged to a large rath recorded under the reference KE058-013. By the time the Ordnance Survey name books were being compiled in the 1840s, the entrance had been deliberately closed off, suggesting the feature was still locally known and perhaps still considered worth sealing, even as its original purpose had long since been forgotten. Whether it was blocked to prevent livestock falling in, or simply tidied away as farmland was reworked, the notes do not say.

Nothing of it remains to be seen at ground level now. The rath itself may still leave some trace in the landscape, as many such earthworks survive as low, grassy rings, often visible only in certain light or from a slight elevation, but the subterranean chamber recorded by nineteenth-century surveyors has left no surface sign. It sits in the archive as a possibility, a cavern with a closed mouth and an uncertain identity.