A souterrain is an artificially constructed underground passage or room, typically built during the early medieval period in Ireland, and used variously for storage, refuge, or both. This particular example is a modest but well-defined space, built from drystone, meaning its walls are assembled from carefully selected stones laid without mortar, relying entirely on their own weight and fit to hold together across the centuries.

The chamber runs on a roughly east-north-east to west-south-west axis and measures 3.3 metres in length, with a maximum width of 1.8 metres and a height ranging between 1.42 and 1.78 metres, making it low enough to require a careful stoop but spacious enough to have served a practical purpose. Entry is from the west-south-west end. It sits within a cashel, a type of early medieval stone-walled enclosure that would have enclosed a farmstead or small settlement, and finding a souterrain within such a cashel is not unusual; the two features frequently occur together across the Irish archaeological record, the underground chamber providing secure, cool storage or an emergency bolt-hole for the people living inside the enclosure above.