What the machine exposed was a souterrain, an underground stone structure of the early medieval period, typically used for storage or refuge, built without mortar using carefully laid dry-stone walling. Two chambers appeared, connected by a passage so tight that even crawling through it would have demanded considerable determination.

The connecting passage between the two chambers measured just one metre in length, but its real obstacle was a porthole slab positioned near the smaller chamber end, its opening only 33 centimetres wide and 33 centimetres high. A porthole slab is a deliberate architectural feature, a stone with a shaped hole cut through it, designed to slow or obstruct an unwanted intruder while someone familiar with the space could slip through quickly. The larger of the two chambers, oriented roughly north to south, measured about 2.5 metres at its longest and 2 metres across, though its roof had fully collapsed by the time of discovery and no entrance could be identified without proper excavation. The smaller chamber, running east to west at 3.2 metres long but barely 1.2 metres wide, was in slightly better condition, its walls rising vertically before inclining inward and meeting a roof of flat stone slabs, though only one of the original three slabs remained in place. The most intriguing find from the site was not a tool or a vessel but a large deposit of shells, mixed into the collapsed debris of the larger chamber, the only material evidence of whoever once made use of the place. Immediately to the west of the souterrain lies a substantial L-shaped earthen bank, over thirteen metres along one axis and sixteen along the other, which may be connected to nineteenth-century field boundaries and dwellings visible on the first edition of the Ordnance Survey map rather than to the souterrain itself.

Only the smaller chamber remains visible today, the larger having lost its roof entirely to the bulldozer's weight and the years since.