This one at Raheens in County Cork was found without any capstones at all, its narrow single chamber deliberately packed with rubble and domestic debris before it was abandoned, which raises more questions than it answers about how and why it was closed off.

A souterrain is a man-made underground structure, typically built using drystone walling, a technique relying on carefully stacked stones fitted together without mortar. The Raheens example sat within a ringfort, the circular enclosure type that served as a farmstead across early medieval Ireland, and measured four metres long, just under a metre wide, and 1.2 metres deep, with stepped access from the eastern end. It came to light in 1989 when archaeologist Anne-Marie Lennon excavated the site ahead of partial destruction by the Sandoz factory. What made the investigation particularly significant was the discovery that the souterrain itself had been constructed over two even earlier structures, suggesting the ground here had been in use across more than one distinct phase of occupation. The deliberate backfilling, combined with the absence of capstones, points to a conscious act of closure rather than simple collapse or decay, though what prompted that decision remains unclear.