What survives is fragmentary but legible to a patient eye: a linear bank, roughly a metre and a half wide and half a metre high, running along the northern and western sides of the outcrop. The northern stretch extends about twenty-five metres, the western about forty, and both contain substantial quantities of stone worked into their fabric. It is the kind of feature that rewards attention precisely because it refuses to announce itself.

The earthwork appears to have functioned in connection with a possible tower house on the same outcrop. Tower houses were the dominant form of fortified residence across Ireland from the fourteenth to the seventeenth centuries, typically comprising a tall, narrow stone tower occupied by a local lord or landowner, often surrounded by an enclosing wall or bawn, a term for the defended courtyard attached to such a structure. The linear bank at Castlefarm, positioned along the more exposed northern and western approaches, may represent the remnants of just such an outer enclosure, defining and protecting the ground around the tower. The limestone outcrop itself would have made for a naturally defensible position, its elevation offering surveillance of the surrounding landscape even if that view is now largely screened by trees. The rubble strewn down the slopes obscures much of what remains, making precise interpretation difficult, though the monument is protected under a preservation order dating from 1976.