Beneath and beneath it, the remains of a cashel, a type of stone-built ringfort enclosed by a dry-stone wall rather than an earthen bank, describe a rough circle about twenty-three metres across. The structure is poorly preserved, much of it collapsed, but where the stonework survives it reveals something worth pausing over: a double wall-facing, meaning the wall was built with two dressed stone faces enclosing a rubble core, a technique that implies a solidity and permanence of intention far beyond a simple field enclosure.

Cashels of this kind were typically built during the early medieval period, serving as defended homesteads for farming families of some local standing. The gap visible at the east-south-east of the Ballybaun example may be the original entrance, oriented to catch the morning light on that east-facing slope. Associated with the cashel is a possible souterrain, an underground stone-lined passage or chamber that in Irish early medieval contexts was used variously for storage, refuge, or both. The site was noted by Fahey as far back as 1893, which places its recognition in the antiquarian tradition that preceded modern archaeological survey, though what Fahey recorded and what survives today are separated by well over a century of agricultural activity and slow collapse. The later field wall laid directly over the cashel wall at the north and south-west is itself a kind of document, showing how the boundaries that mattered to earlier inhabitants were quietly absorbed into the working landscape of later farming generations.