The site belongs to a category of monument that tends to survive quietly in the Irish landscape for well over a thousand years, only to meet its end through modern agricultural practicalities.

A souterrain is a man-made underground structure, typically stone-lined or earth-cut, associated with ringforts and used variously for storage, refuge, or both. The chambers at Coolbane were of the earth-cut variety, carved directly into the subsoil rather than built from stone. They were recorded as intact, and apparently consisting of several distinct chambers, when somebody examined them in August 1934, a visit captured in files held by the National Museum of Ireland and later cited by McCarthy in 1977. At that point the ringfort that contained them was still a coherent monument. Sometime in the 1970s or early 1980s, however, the construction of a slurry pit within the ringfort's interior destroyed the chambers. The date is not precisely known; it comes from local information rather than any formal record, which itself says something about how quietly these losses happen.

What remains today is the ringfort itself, a circular enclosure defined by its banks and ditches, the kind of settlement form that was common across Ireland during the early medieval period. The souterrain it once sheltered is gone, leaving the site as a slightly hollowed-out version of what it was, a monument that has survived on the surface while losing the most archaeologically unusual thing about it underground.