This is a rath, the Irish term for a ringfort, the kind of enclosed farmstead that was built across Ireland in the early medieval period, roughly between the fifth and twelfth centuries. Thousands survive in various states of preservation, yet each one carries the faint outline of a domestic world: a family, their livestock, their boundary between the known and the open countryside.

This particular example at Ballynacor measures approximately 34 metres north to south and 31 metres east to west, giving it a slightly compressed, sub-circular shape rather than a perfect ring. The enclosing bank is composed of earth and stone, and there was once an external ditch running around it, though that feature has been largely filled in along the north-western to eastern arc. The interior rises gently toward its centre, a common characteristic that can result from centuries of accumulated occupation material or simply from the original ground level being built up within the bank. A gap on the eastern side is interpreted as a possible original entrance, east-facing entrances being a recurring feature in Irish ringfort construction, possibly for reasons of orientation toward the morning sun or simply prevailing practical habit.