But they are almost certainly the collapsed or partially buried roof of a souterrain, an underground stone-built passage or chamber used in early medieval Ireland for storage, refuge, or both, and their presence here in low-lying grassland at Fearagha hints at a much larger complex beneath the soil.

The slabs sit within a cashel, a type of early medieval enclosure defined by a drystone wall rather than an earthen bank. This one is roughly subcircular, measuring approximately 60 metres north to south and 50 metres east to west, which makes it a substantial enclosure. Its drystone wall survives from the north-north-east around through the east to the south-south-west, while the western side is marked instead by a low natural or man-made scarp; elsewhere, later field walls have been built directly on top of the original enclosing element, absorbing it into the farmed landscape. Quarrying has eaten into the monument at its northern end, so the full original extent is difficult to judge. Just outside the cashel wall at the south-south-west, there is also a shallow stone-lined hollow measuring roughly three metres east to west and one and a half metres north to south, the purpose of which is unclear but which may have served a functional role connected to the settlement. A second ringfort, a related class of early medieval enclosed farmstead, lies only 150 metres to the south, suggesting this corner of County Galway was reasonably well settled during the early historic period.