What they were recording was almost certainly a collapsed souterrain, an underground stone-lined passage of the kind built throughout early medieval Ireland, typically for storage or refuge. Today the structure has lost its roof entirely, and what remains is a stony, nettle-choked hollow pressing into the western half of a ringfort, the circular earthwork enclosure that once formed the defended farmstead of which this underground chamber was a part.

The hollow follows an L-shaped course across the ground. Its longer arm, running roughly east to west, extends about fourteen and a half metres before turning sharply southward, where a second arm of around ten metres continues on a north-south axis. The full length of the depression runs to around twenty-four and a half metres, with a width of roughly three and a half metres and a depth of up to one metre at its deepest point. These proportions, and the right-angle turn, are consistent with souterrains elsewhere in Ireland, which were often built in segmented or angled layouts, possibly to baffle draughts, to confuse intruders, or simply to follow available ground. The association with a ringfort is equally typical; the two features frequently occur together across the Irish landscape, suggesting the souterrain served the household that occupied the enclosure above.