It is a souterrain, an underground or semi-underground passage or room constructed from dry stone, roofed with flat capstones, and used in early medieval Ireland variously for storage, refuge, or purposes that archaeologists still debate. This one runs roughly east to west, measures about 5.8 metres in length, 1.4 metres across, and just over a metre in height, which means entry was never a casual affair. At the western end, a creepway, a deliberately low connecting passage designed so that only one person could pass through at a time, has been blocked, sealing off whatever lay beyond.

The cashel it belongs to is a stone-walled ringfort, the kind of enclosed farmstead that dots the Irish landscape in the thousands, though most are far less intact than people expect up close. Souterrains like this one were commonly built within such enclosures, and the combination of a defensible outer wall and a concealed underground chamber suggests the kinds of anxieties, about raiders, rival clans, or simply a harsh winter, that shaped daily life in early medieval rural Ireland. The measurements here are modest but functional. A chamber nearly six metres long would have held a reasonable quantity of goods, or a small number of people in an emergency. The blocked creepway adds a particular quality to the place; something was once accessible from that western passage, and at some point the decision was made to close it off permanently.