The feature in question is a souterrain, an underground stone-lined tunnel typically associated with early medieval ringforts, used variously for storage, refuge, or both. This one, at Cloghardeen, has been covered over, its entrance now little more than a depression in the southern quadrant of an otherwise unremarkable earthwork sitting in an agricultural field.

The ringfort itself, known as a rath, is a roughly circular enclosure just over thirty-four metres in diameter, defined by an earthen bank that would once have enclosed a farmstead, most likely dating to the early medieval period between roughly the fifth and twelfth centuries. The bank survives to a height of nearly a metre on the exterior in places, though it is considerably slighter on the interior. What makes the site a little unusual is the evidence of later disturbance: the eastern section of the original bank has been replaced by a stone wall, suggesting the site was reused or modified at some point after its initial construction. More striking still, the interior in that same eastern quadrant appears to have been quarried into, with the displaced material heaped up around the edges. In the northern quadrant a shallow external fosse, essentially a ditch running outside the main bank, is still faintly visible, roughly two metres wide and thirty centimetres deep. Modest dimensions, but enough to suggest the enclosure once had at least a token outer boundary.