The entrance gives onto a creepway, a narrow underground passage just wide enough to crawl through, which slopes downwards to the north-west and disappears into the dark. As of the last recorded account, it remains unexplored.

Souterrains are underground stone-built passages or chambers associated with early medieval settlement in Ireland, typically constructed between the seventh and twelfth centuries. They are most often found in association with ringforts, the circular enclosed farmsteads that once formed the basic unit of rural life across the Irish countryside. Their precise function is still debated, though cool storage and refuge during periods of threat are the most commonly proposed explanations. The Derryleigh example sits within the north-western quadrant of a ringfort, following a pattern seen at comparable sites around the country. What distinguishes it, or rather what makes it quietly arresting, is the straightforward fact recorded about it: the creepway slopes down and away, and no one has gone in.