The depression follows the inside of an earthen bank, and what it traces is the likely collapse of a souterrain, one of those stone-lined subterranean tunnels built during the early medieval period, most commonly associated with ringforts, that served variously as storage spaces, refuges, or places of concealment.

The souterrain sits within the north-western quadrant of a ringfort, a type of enclosed farmstead defined by a circular bank and ditch that was the standard form of rural settlement in Ireland from roughly the fifth to the twelfth centuries. The exposed section of the passage measures 3.5 metres in length and 1.2 metres in width, and it may represent the original entrance rather than a cross-section of the full structure. The construction is typical of its kind: flat stone lintels laid across the top to form a roof, and side walls built using drystone corbelling, a technique in which small boulders are layered inward and upward without mortar, the stones angled so that each course slightly overhangs the one below. To the south-west, that sunken line running along the bank suggests the passage extended further before it fell in, leaving only the ground's surface to hint at what lies beneath. The whole feature sits on a slight rise, which would have offered both drainage and a degree of natural defensive advantage to whoever built and used it.