This subterranean passage, built using traditional drystone construction techniques, runs east to west and showcases the impressive engineering skills of our ancestors. The structure features massive stone lintels supporting the roof, demonstrating the builders' understanding of weight distribution and structural integrity, even without the use of mortar.

When discovered, the souterrain's floor was filled with centuries of collapsed earth, suggesting it had been abandoned and forgotten long ago. These underground passages, found throughout Ireland but particularly common in Ulster, were typically built between the 6th and 12th centuries AD. They served various purposes; some archaeologists believe they were used for food storage, taking advantage of the cool, stable temperatures underground, whilst others suggest they may have provided temporary refuge during raids or served ceremonial functions within early medieval communities.

Rather than excavate the site fully, the landowner has chosen to re-bury this ancient structure, preserving it for future generations. This decision reflects a growing understanding that sometimes the best conservation method is to leave archaeological features undisturbed in their protective soil blanket. The souterrain at Killymasny joins hundreds of similar structures across Ireland, each one a tangible link to the ingenious ways our ancestors adapted to their landscape and the challenges of medieval life.