You could walk across the ground and have no idea they existed, which is more or less what happened for centuries until their discovery in 1975.

The structure is a souterrain, a type of underground passage or chamber system built, usually in early medieval Ireland, from stone or by cutting directly into the earth. The Dromdaleague example is earth-cut rather than stone-lined, and consists of two partially infilled chambers connected by a creepway, the narrow low passage that links souterrain chambers and would have required anyone passing through to crawl. A second possible creepway was identified leading off the first chamber but has not been fully explored. The souterrain lies to the north-east of a church within the graveyard, a relationship between souterrain and ecclesiastical site that is not unusual in the Irish archaeological record; early church settlements sometimes made use of such underground spaces for storage or refuge. Beyond the 1975 discovery date and the basic layout of the structure, the history of who built it and when remains unresolved.

There is nothing to see at ground level, and the partially infilled state of the chambers means access is not a practical matter for the casual visitor. The interest here is almost entirely in the fact of the thing, an unassuming patch of graveyard ground concealing an unexplored underground passage that has not been fully examined since it was found.