The depression runs for twelve metres, is just over three metres wide, and dips less than a metre below the surrounding ground. It is a modest feature, easy to overlook, but the ambiguity surrounding it is what makes it worth a second thought.

The trench sits within a rath, the Irish term for a roughly circular enclosure, typically defined by an earthen bank and ditch, that served as a defended farmstead during the early medieval period, broadly from the fifth to the twelfth centuries. The depression extends from the inner face of the southern bank in a northward direction, which is a configuration that would be consistent with a souterrain, an underground stone-lined passage or chamber that was often built within or beside a rath to provide storage, refuge, or ventilation. Souterrains were usually roofed with large flat stones and then covered over, and when those roofs eventually collapse, the ground above can sink into exactly this kind of linear hollow. The difficulty at Ballinteane is that the same shape could equally have been produced by quarrying, whether for stone, gravel, or some other material. The evidence, such as it is, does not settle the question either way.