The roof has collapsed, leaving a shallow trench visible on the surface, its edges studded with protruding stones and its floor scattered with loose rubble. Hazel roots have worked their way in, threading through what was once a deliberate, enclosed space. What you are looking at is a souterrain, a type of man-made underground tunnel or chamber commonly associated with early medieval Irish ringforts, typically used for storage, refuge, or both.

The souterrain sits within a rath, the Irish term for a ringfort, a circular enclosure defined by an earthen bank or scarp, of the kind built and inhabited across Ireland roughly between the sixth and twelfth centuries. This particular rath at Carrowgallda preserves its interior rise clearly enough that the collapsed souterrain can still be traced as a distinct depression running east to west for about 13.5 metres before turning south for a further 5 metres, where it narrows slightly from around 2.6 metres to 2.4 metres in width and becomes shallower. The L-shaped plan is characteristic of how souterrains were often designed, with turns and changes in level thought to serve a defensive or concealment function. The gradual narrowing toward the southern end may reflect differential collapse as much as original construction, but the overall form of the passage remains legible at the surface.