The depression measures roughly sixteen metres long and fourteen metres wide, running east to west, and sinks no more than a metre and a half at its deepest. To a passing eye it reads as an unremarkable dip in the field. To anyone who knows what to look for, it marks the collapsed roof of a structure that once served a very deliberate purpose.

Souterrains are underground stone-lined passages or chambers, typically associated with early medieval settlement in Ireland, roughly the period from the sixth to the twelfth century. They were constructed beneath or beside ringforts and other settlement enclosures, and are thought to have functioned as places of refuge, cool storage, or both. The Corbally example, recorded on the basis of local information and compared in character to a known souterrain nearby, appears to have had two chambers, a configuration that is not uncommon. The collapse of the roof is the usual fate of these structures once the stone corbelling or lintels that support them give way, leaving precisely this kind of grassy hollow as the only surface trace. The site sits in ordinary farmland, with nothing to announce its presence beyond the slight change in ground level.