The surface gives almost nothing away, and whatever larger pattern these earthworks once formed has long since blurred into confusion. That ambiguity is part of what makes the site quietly compelling: below ground, the structure is precise and deliberate, even as the land above it has lost its legibility.

A souterrain is an underground stone-built passage or chamber, typically associated with early medieval settlement in Ireland, and thought to have served for storage, refuge, or concealment. The one at An Mhín Aird Thiar follows a roughly L-shaped plan, with a north-south passage leading via a tight creepway into a smaller east-west chamber. The passage, just under two and a half metres long and less than a metre wide, is entered by a sloping ramp down from ground level, through an opening barely wide enough to admit a crouching adult. Its drystone walls are slightly corbelled, meaning they lean inward toward the top, and four large capstones close the roof overhead. The creepway connecting passage to chamber is roofed with a single slab. The chamber itself, built partly of upright slabs with drystone walling above, is a little more generous, rising to one and a half metres, though its western wall has since collapsed. There was formerly a local tradition that a ringfort, a type of enclosed farmstead widespread in early medieval Ireland, once occupied the site above, which would place this souterrain in a familiar and well-understood context. That tradition, however, no longer survives, and the surface remains are now too disturbed to confirm or contradict it. The detailed measurements and description were recorded by J. Cuppage in the 1986 Dingle Peninsula archaeological survey, a landmark study of the Corca Dhuibhne region.