The one at Inchingerig in County Cork came to light not through deliberate excavation but by accident, when construction work on a farmyard in 1991 broke through into something that had gone unnoticed for centuries beneath the soil.

What the builders uncovered was a sequence of four earth-cut chambers connected by creepways, the narrow low passages, sometimes little more than half a metre wide, that a person would have to crouch or crawl through to move between spaces. The layout is a compact but careful one. Chamber 1 opens into Chamber 2 via a creepway at its south-eastern end, and Chamber 2, which was considered too unstable to enter safely, still revealed a blocked-up construction shaft in its eastern wall, a detail that offers a glimpse of how these structures were originally built, sunk from above and then sealed. From Chamber 2, another creepway leads south into Chamber 3, a notably small space just under a metre across at its widest, and from there a further short creepway connects into Chamber 4, the largest of the sequence at roughly three metres in length. In the northern end of Chamber 4, bedrock breaks through the floor, and there is a possible second construction shaft overhead, suggesting this end of the souterrain was cut down to the natural rock rather than shaped entirely in earth or subsoil.

The dimensions throughout are close and deliberate. Nothing about the design is casual. The narrowness of the creepways, some less than half a metre wide, would have made pursuit or forced entry difficult, and that defensive logic is a recurring feature of souterrains across Ireland. That a structure so carefully engineered survived undetected until a farmyard digger reached it in 1991 is, in its quiet way, a reminder of how much of the early medieval landscape still lies just out of sight.