The hollow, roughly 7.9 metres long and 2.3 metres wide, running roughly north-north-west to south-south-east, is consistent with what archaeologists call a souterrain, an underground stone-lined tunnel or chamber built during the early medieval period, typically beneath or beside a settlement. These structures served various purposes, most likely food storage, given their cool and stable temperatures, though they could also offer a degree of refuge. At Garrauns in County Galway, nothing has been excavated, and the designation remains tentative.

The hollow sits within a circular rath, a type of enclosed farmstead common across early medieval Ireland, defined here by an inner scarp, an intervening fosse, and an outer earthen bank. The enclosure measures around 37.5 metres in diameter and survives in fair condition, though a later field wall has been built across the outer bank, running from the south-west around through the west and continuing to the north-east, the kind of quiet agricultural overwriting that happened on countless sites across the country as working land absorbed older monuments. Two gaps in the enclosure, one to the south-east and one to the south-south-east, may represent original entrances, though without excavation that too remains uncertain. The site sits on a rise in undulating grassland, which would have made practical sense for its original occupants, offering visibility and drainage in equal measure.