The rath at Lisnafinnoge measures 33.5 metres in diameter and survives in fair condition, which, given the pressures of centuries of agriculture, is notable in itself. What makes it slightly more unusual is the presence of a souterrain, or corbelled underground gallery, within the north-eastern quadrant of its interior.

A rath is a roughly circular enclosure defined by an earthen bank and, often, an external ditch, used during the early medieval period in Ireland, broadly from around the fifth to the twelfth century, as a farmstead for a family of some local standing. Thousands survive across the island in varying states of repair, but each one represents a specific household, a specific patch of land, and a specific set of decisions made by people whose names are almost entirely lost to us. The souterrain associated with this example, recorded under the reference GA098-099001, is the kind of feature that raises questions a rath on its own does not. Souterrains are stone-lined underground passages or chambers, typically interpreted as places of refuge or cold storage, and their construction required considerable effort and planning. Finding one within the north-eastern interior of this particular enclosure suggests a degree of investment in the site that goes beyond the merely functional.