The depression is subtle enough that a casual visitor might walk across it without a second thought, yet its distinctive shape is the kind of detail that makes archaeologists pause.

The hollow sits within a rath, a circular earthen enclosure that served as a farmstead during the early medieval period, roughly from the fifth to the twelfth century. These enclosures were once among the most common features in the Irish rural landscape, and souterrains were frequently built within them, their corbelled or lintelled roofs now long since fallen in. At Traskernagh, the collapse of whatever passage once existed has left only that angular indentation in the earth, an L-shape that corresponds loosely to the plan such underground structures typically followed.