It runs north-north-west to south-south-east, stretches just over seven and a half metres in length, and stands tall enough for a person to move through without crouching. This is a souterrain, a type of underground stone-built structure found widely across early medieval Ireland, typically associated with settlement sites and thought to have served as places of refuge, cool storage, or both.

The souterrain sits within the south-west sector of a cashel, which is a roughly circular enclosure defined by a drystone wall, used in early medieval Ireland as a farmstead or defended homestead. The passage itself is rectangular and built entirely in drystone, meaning the stones are laid and fitted against one another without any binding material. What makes it particularly legible as a piece of construction is the survival of its ventilation details. An air vent measuring roughly sixty centimetres wide and fifteen centimetres high is visible in the north-east side-wall, positioned about two and a half metres from the entrance at the south-south-east end. A second possible vent of similar proportions appears approximately midway along the same wall. These openings would have allowed air to circulate within the passage while keeping the interior dark, cool, and largely sealed from the outside.