The construction work in 1983 broke through into a structure that had lain undisturbed beneath ordinary pastureland, its existence entirely unknown until a digger or spade changed that.

What the Ikerrin Survey recorded was a carefully built underground corridor, just over seven metres long, roughly a metre high, and half a metre wide, running on a northeast to southwest axis. Its roof consisted of lintels, large flat stones laid horizontally across the top, and its side walls were drystone construction, meaning dry-laid without mortar, held together by careful placement and the weight of the earth above. The whole thing sat only about sixty centimetres below ground level, which makes it slightly surprising it survived as long as it did without disturbance. Souterrains of this type are generally dated to the early medieval period and are thought to have served as cool storage spaces, refuges, or both, usually associated with a nearby settlement or ringfort that may have long since disappeared from the landscape above.