It survives only as a notation on a map drawn in 1842, where surveyors of the Ordnance Survey recorded a small square enclosure, roughly twenty metres on each side, using the hachured lines that indicate an earthwork with raised banks. At some point between that survey and the present, the feature was levelled, most likely by agricultural improvement, and the pasture that now covers the slope gives no indication that anything was ever there.

Enclosures of this kind are among the most common archaeological features in the Irish countryside. They typically date from the early medieval period, though some are earlier, and they served a range of purposes, from farmstead boundaries to ceremonial or funerary spaces. The square plan at Killeena is worth noting; most surviving enclosures in Ireland are circular or subcircular, and a rectilinear form can suggest a different date or function, though without excavation it is impossible to say more. What the 1842 map preserves, then, is a brief documentary glimpse of a feature whose origins remain entirely unknown, caught just before it disappeared from the landscape altogether.