What little can be seen from above suggests a stone-lined underground chamber, its ceiling formed from flat capstones laid horizontally as lintels, running eastward into the dark. The passage is inaccessible, so the chamber's full extent remains unknown, though two depressions in the ground a short distance to the east hint that the structure continues further and that sections of it may have already collapsed beneath the surface.

Souterrains are underground passages or chambers built, most commonly, during the early medieval period in Ireland, roughly between the seventh and twelfth centuries. Their exact purpose has long been debated; they are generally thought to have served for storage, where the constant underground temperature would help preserve food, or possibly for refuge in times of threat. They are frequently found in association with ringforts, the circular enclosed farmsteads that were the dominant settlement form of early medieval Ireland, and this example at Gleann Daimh follows that pattern precisely. The ringfort it belongs to sits close by, and the souterrain was evidently constructed as part of the same domestic complex. The construction method here, stone-lined walls and lintel roofing, is typical of Cork and Munster examples, where suitable flat stone was more readily available than in some other parts of the country.

Because the opening is too narrow to enter and much of the structure lies sealed underground, there is limited practical access to the site itself. The two ground depressions to the east are perhaps the most visible indication that something significant runs beneath the surface, and they serve as a quiet reminder that early medieval life in this part of Cork left traces that are still settling, slowly, into the earth.