The more northerly of the two survives as a roughly circular earthwork about twenty-eight metres across, its bank still reaching nearly a metre and a half on the exterior side, though considerably less within. A shallow fosse, the defensive ditch that typically runs around the outside of such structures, traces part of its perimeter.

Ringforts, sometimes called raths when formed from earth rather than stone, were the dominant settlement form in early medieval Ireland, built and occupied roughly between the fifth and twelfth centuries. They served as enclosed farmsteads, the bank and fosse providing a degree of security for a family and their livestock rather than functioning as military fortifications in any serious sense. The one at Glennahulla shows the kind of quiet attrition that centuries of agricultural use can inflict: quarrying has disturbed the bank to the south-east, and the southern and south-western sections have disappeared beneath accumulated overgrowth. The interior is similarly obscured, which means that whatever features may once have been legible on the ground, post-holes, souterrains, or traces of structures, are not easily visible today.