They came to light in 1978, the kind of discovery that tends to happen by accident, a disturbance of ground that turns out to be something far older than expected. What was found was a souterrain, an earth-cut underground passage or chamber system used in early medieval Ireland, typically for storage, refuge, or both. This one consists of not one but two distinct chambers, their shapes subtly different from each other, which gives the structure a slightly irregular, almost improvised character.

The two chambers were recorded by Ó Drisceoil and Hurley in 1978. The first is roughly circular, measuring approximately 2.5 metres in length, 2.3 metres in width, and just a metre in height, low enough that any adult would need to crouch. The second chamber is oval, a little longer at 3.5 metres and slightly narrower at 1.7 metres, with a ceiling height of 1.2 metres. Both are earth-cut rather than stone-lined, which places them among the simpler end of souterrain construction, dug directly into the subsoil rather than built up with drystone walling. The difference in shape between the two chambers is worth pausing on. Souterrains were rarely uniform; they were practical structures, shaped around what the ground allowed and what the builders needed, and the shift from circular to oval here suggests the work of people solving problems as they went.