This is a souterrain, an underground or semi-subterranean tunnel of early medieval Irish construction, typically used for storage, refuge, or both. What makes this particular example quietly unusual is that it sits not beneath open ground but folded into the thickness of the cashel wall itself, its drystone sides corbelled inward, meaning the stones are stepped gradually towards one another as they rise, narrowing the space overhead. Many of the large roofing slabs that once sealed it have since gone missing.

The cashel here is known as Caher Conor, or Cathair na gConchúrach, a sub-oval stone enclosure whose enclosing wall and interior have both changed considerably since the site was first noted in the nineteenth century. Five structures of varying preservation now occupy the interior, though earlier accounts suggest others were once visible. A second passage, roughly L-shaped in plan and considerably smaller at around 0.7 metres wide by 0.75 metres high, opens near the western end of the north wall and leads toward a large clochaun, a corbelled stone building, in the interior. Unlike the main souterrain, this second passage has its roofing slabs resting directly on upright orthostatic side walls rather than on corbelled courses. The site was surveyed and documented by J. Cuppage in the 1986 Dingle Peninsula archaeological survey of Corca Dhuibhne.