The entrance, just 1.2 metres wide and 0.8 metres high, drops into an earth-cut chamber with a rounded roof. Beyond that point, the way is blocked by soil heaved up by badgers, and a series of depressions and a section of collapse on the surface hint at where the passage continues, trending south-westward for at least twelve metres before, according to local memory, it once emerged on the bank of a nearby river.

The structure is a souterrain, an underground passage or chamber cut into the earth and typically associated with early medieval ringforts. It sits within a rath, which is one of the most common archaeological features in the Irish landscape, a circular enclosure defined by an earthen bank and ditch, used as a farmstead from roughly the sixth to the twelfth century. Souterrains within raths are well documented across Ireland and are thought to have served as places of refuge, cool storage, or both. What makes the Curragh example quietly compelling is the layer of living memory that clings to it. Local people remember, as children, crawling the full length of the passage and emerging at the river's edge, a distance of around fifteen metres. That exit, if it still exists as a physical space, is now underground and out of reach, sealed off as effectively by badger activity as any deliberate backfilling.