They recorded it as a complete circular earthwork, roughly thirty metres across, using the hachured lines that mapmakers of the period used to indicate an embanked enclosure on the ground. By 1903, only the northern arc was still legible on the maps, and that partial survival has remained more or less constant since.

The site is a rath, the Irish term for a ringfort, the most common archaeological monument type in the Irish landscape. These were typically enclosed farmsteads of the early medieval period, their circular earthen banks defining a domestic space for a family and their livestock. The Ballymacoo example sits in pasture about a hundred and fifty metres east of the Owennagearagh River, and what remains is an arc of around twenty-six metres, running from west to east-south-east. The earthen bank, standing about one and a quarter metres high, has been capped with a stone wall at some point and folded into the surrounding field fence system, which is precisely why it has survived at all. Being made useful is what saved it from being levelled entirely, even as the rest of the circuit disappeared.