The mound is modest, barely a metre high and roughly seventeen metres across at its widest, but at its crown sits a shallow circular depression about four metres in diameter, the kind of subtle surface feature that archaeologists learn to read as a sign of something hollow beneath.

A souterrain is an artificially constructed underground passage or chamber, typically built during the early medieval period in Ireland, often beneath or beside a ringfort or cashel. A cashel is a stone-walled enclosure of the same era, the drystone equivalent of the more familiar earthen ringfort. The combination here, a souterrain within a mound within a cashel, points to a settlement of some consequence. According to research recorded by Nyhan and cited by McCarthy in 1977, the souterrain's walls stood 1.37 metres high, suggesting a passage of reasonable proportions rather than a simple crawlspace. Souterrains were used for a variety of purposes, including storage of dairy produce in their cool, stable interiors, and possibly as places of refuge during raids. The fact that this one sits within a cashel, itself a defensive or high-status enclosure, adds a layer of social complexity to what outwardly appears to be an unremarkable grassy hump in a Cork field.