A 1936 Ordnance Survey map marked a souterrain, an underground passage or chamber typically built in the early medieval period for storage or refuge, to the west of this ringfort's interior. Today, nothing on the surface gives it away. The fort itself, however, remains legible in the landscape: a circular raised platform roughly thirty metres across, wrapped by an earthen bank that still stands about 1.2 metres high above a low outer scarp.

Ringforts, known in Irish as raths when built primarily from earth and bank rather than stone, were the standard farmstead enclosure of early medieval Ireland, broadly from the fifth to the twelfth centuries. The one at Ballyogaha sits on a south-southwest-facing slope, positioned just above a steep incline, and commands a clear view from east through to north-northwest. That positioning was deliberate: visibility and defensibility mattered, even for what were likely civilian farmsteads rather than military strongholds. The bank is broken by gaps on the east-northeast to east-southeast arc, to the southwest, and to the northwest, which may reflect original entrances or later disturbance. The interior tilts gently downhill toward the south-southwest, following the natural lie of the slope.

The missing souterrain is the quietly strange detail here. These underground features are found at hundreds of Irish ringforts, often running just beneath the surface in stone-lined or rock-cut passages, yet they leave almost no mark above ground once their roof material has settled or collapsed. The 1936 map recorded its presence, but subsequent survey found no visible trace remaining. It may be entirely intact below the soil, or largely gone. Either way, the ground at Ballyogaha holds at least one thing that the eye cannot reach.