The entrance to a souterrain sits exposed in the earthwork, framed by a lintel and a pair of jamb stones, the opening just 56 centimetres high and 90 centimetres wide. Whoever recorded it noted simply that it did not prove possible to access the souterrain itself, and left the matter there.

A souterrain is an underground passage or chamber, typically stone-lined, built during the early medieval period and associated with ringforts, the circular enclosed settlements that dot the Irish countryside in their thousands. They were used variously for storage, refuge, and ventilation, and their entrances were often deliberately narrow, enough to slow an intruder considerably. This one belongs to the Creevymore rath, the earthen ringfort with which it is associated, and its entrance stones survive intact, which is itself worth noting. Many souterrains across Ireland have been robbed of their structural stonework over the centuries, their lintels carted off for walls and buildings elsewhere. Here the frame remains, low and deliberate, opening into a darkness that has not been formally investigated.