That the fence also marks the boundary between two townlands, Ballynacor and Martinstown, only adds a certain irony: a line drawn in relatively recent times now bisects something that was old when those townland names were new.

The earthwork itself is a rath, the Irish term for a roughly circular enclosure defined by an earthen bank and an outer fosse, which is a shallow drainage or defensive ditch. Raths were typically built during the early medieval period and served as enclosed farmsteads, though their precise function varied by site. This one sits on the south-east facing slope of a low hillock, positioned to take in open views across the landscape to the south and south-east. Its roughly circular outline stretches approximately 38 metres along its north-east to south-west axis, with a bank of earth and stone reaching a maximum height of about one metre and a shallow fosse running outside it. The original entrance, a narrow gap just under one and a half metres wide, faces west-south-west. Inside, the ground slopes gently from north-north-east down to south-south-west, and several depressions are visible across the interior surface, the kind of subtle unevenness that often signals the collapsed remains of internal structures or later disturbance, though their exact origin here is not recorded.