What was once a self-contained defended settlement is today legible mainly as a scarp, the remnant of an original earthen bank, curving from south through west to north around the summit of the rise.

A rath, to use the Irish term, was a roughly circular or oval enclosure defined by one or more earthen banks and ditches, typically enclosing a farmstead or the residence of a person of modest local standing during the early medieval period, roughly the fifth to twelfth centuries. The Glenaclara example is slightly unusual in being subrectangular rather than circular, measuring approximately 36 metres on its east-west axis and 25 metres north to south. It appears on the 1838 edition of the Ordnance Survey six-inch map, which recorded the enclosure before the field boundaries along its southern and western sides had fully overwritten it. By the time anyone looked again in detail, those boundaries had settled into the landscape as if they had always been there, and the external scarp is now the clearest physical trace that something older lies beneath the present arrangement of fields.