It is a souterrain, an early medieval underground passage built from dry-laid stone, typically used for storage or refuge, and what remains of it now is considerably less than what once existed. Local memory holds that in the 1950s much of its stonework was carted away for building material, a fate that has befallen more than a few such structures across Ireland.

The mound itself is known locally as Cnocán na h-Aitinne, and it is a natural feature rather than a man-made one, a peat-covered rock outcrop rising about two metres above the surrounding boggy pasture. What makes the setting more interesting is that three pre-bog walls radiate outward from the mound at the northwest, northeast, and southeast, fragments of a wider field system that predates the blanket bog now covering much of the landscape. The souterrain sits at the base of the mound's southeastern side. Two short passages can still be identified: the first runs east to west and is capped by two large lintels resting on upright slabs, measuring just under a metre in length; a small aperture in the surface gives a view down into the second section, slightly longer and oriented west-southwest to east-northeast, though it is largely choked with stone debris. An elongated depression continuing for some six and a half metres to the north-northeast may well be the footprint of a destroyed passage, though nothing conclusive remains. One object survived the general dispersal intact: a grooved whetstone, a sharpening stone with a channel worn into its surface by repeated use, was recovered from the souterrain and is now held by the National Museum of Ireland.