What lay beneath was a stone-built underground chamber, carefully corbelled and roofed, sitting in reclaimed pasture above the Glennacroghery Stream. It had survived intact not because anyone knew it was there, but because the earthwork around it had, until that point, been left alone.

The discovery came about when a landowner, Mr Gubbins, undertook levelling works on a low-lying area of his land. He wanted to fill in a depression of roughly a metre to the north-east, possibly an old ditch between an inner and outer bank of the adjacent enclosure, or perhaps a natural hollow following an old watercourse. During the machine work, a capstone was displaced, and archaeologist Celie O'Rahilly was called to record what had been uncovered. The chamber she described is rectangular, aligned south-west to north-east, measuring 2.4 metres in length at roof level, 1.3 metres wide, and roughly 1.1 metres in visible height. Its walls are built from at least six courses of rounded stones, topped with flat corbels, those projecting stones that support a roof without mortar, with three large slabs laid across the top to form the ceiling. A souterrain, to give the structure its proper name, is a type of man-made underground passage or chamber associated with early medieval settlement in Ireland, typically built within or close to a ringfort or enclosure. The enclosure here lies just 40 metres to the south, lending weight to that identification. A low cavity extending southward from one end of the chamber hinted at further extent, and the north-east end remained partially obscured by a ramp of soil thrown up during the levelling. Animal bone, charcoal flecks, and burnt clay were found on the surface nearby, suggesting the broader site had seen sustained occupation.

The site sits in agricultural land and is not formally set up for visitors. The area around the Glennacroghery Stream is quiet farming country, and the earthwork associated with the souterrain was already largely levelled at the time of discovery. Anyone with a serious interest would do better to consult the National Monuments Service record before making any approach, and to bear in mind that the chamber was disturbed during the levelling works, with the original capstone broken in the process. What remains is fragmentary but genuinely unusual, a small, carefully built space that only came to light because a farmer wanted to flatten a dip in his field.