On its own, such a feature would be easy to step over without a second thought. But its position, extending inward from a break in the bank of the enclosure, points to something that once ran beneath the surface: a souterrain, or at least what remains of one.

Souterrains are underground passages or chambers, typically built during the early medieval period in Ireland, and usually associated with ringforts and raths. They were constructed from stone, timber, or a combination of both, and are thought to have served as places of refuge, cool storage for dairy produce, or both. Over time, as the roof structures collapsed and the earth settled, many reduced to exactly what survives here: a surface depression that preserves the outline of something that was once fully enclosed. The rath at Dinginavanty is a related feature, a rath being a roughly circular earthen enclosure, common across the Irish landscape, that typically surrounded a farmstead during the early medieval centuries. That the souterrain appears to open from a gap in the bank into the interior of the rath is consistent with how these underground features were typically accessed, discreetly, from within the protected space of the enclosure itself.