This circular fortification, measuring 25 metres in diameter from north to south, sits on a raised platform that’s most pronounced on its northern side, where the defensive scarp rises between 1.5 and 2 metres high. As you move around to the southern edge, this earthwork gradually diminishes until it barely rises above the surrounding ground level.

The castle’s defensive features include traces of an external fosse, or dry moat, that would have provided an additional layer of protection for its medieval inhabitants. This ditch, measuring 2.5 metres wide and about half a metre deep, is now only visible along the western to southwestern sections of the site. Archaeological evidence suggests a ramped entrance once existed on the south-southeast side, spanning approximately 9 metres in width; this would have been the main access point into the fortified enclosure.

Ringwork castles like Knockanavar were typically built by the Anglo-Normans in the late 12th and early 13th centuries as they established their presence across Ireland. Unlike the stone castles that would follow, these earthwork fortifications consisted of a raised circular or oval platform surrounded by a timber palisade, with the earth bank and ditch providing the primary defensive elements. Though less imposing than their stone successors, ringworks were quicker to construct and served as important administrative and military centres during the early stages of Norman settlement in Ireland.