The ground drops away steeply on three sides, south, east, and west, so that whoever built here was letting the topography do much of the work. It is a practical, almost austere choice of location, and it tells you something about how these sites functioned.

A ringfort, or rath, is an enclosed farmstead of the early medieval period, typically dating from roughly the fifth to the twelfth century, defined by one or more circular earthen banks and ditches. At Ballinacrow, the enclosure is roughly circular with a diameter of about 27.5 metres. The earthen bank that defines it is poorly preserved, measuring three to four metres wide but only about a quarter of a metre high, so the structure has largely melted back into the hillside over the centuries. A faint trace of an external fosse, the ditch that would once have reinforced the bank, survives on the northern side, which is the one approach where the natural slope offered no protection. No entrance is visible today, and no internal features have been recorded, leaving the interior as an open, grassy circle with little to betray its age.