The word "may" is doing significant work in that sentence. Local tradition holds that a cave or souterrain lies within the earthwork, but no survey has recorded its dimensions, its layout, or even its precise position. The ground above shows no visible trace.

A souterrain is an underground stone-lined passage or chamber, typically associated with early medieval settlement in Ireland, and usually found in connection with a rath, which is a circular earthen enclosure that served as a farmstead during the same period. The pairing of the two is not unusual; souterrains were commonly used for food storage or as places of refuge. What is unusual here is the complete absence of corroborating evidence beyond oral tradition. No excavation has been recorded, no collapse in the ground surface points to a hidden void below, and no historical document appears to confirm the local account. The rath itself is a real and recorded feature. The souterrain, for now, exists only in what people have passed on by word of mouth.