The site commands wide views to the north and south, and that visibility was almost certainly the point. This is a rath, a type of ringfort that once served as an enclosed farmstead during the early medieval period in Ireland, typically consisting of a raised interior surrounded by one or more banks and ditches. What survives at Ballynacarhagh is modest but legible enough to reward a careful eye.

The rath measures approximately 36 metres east to west and 31 metres north to south, making it a reasonably substantial example of the type. It is defined by an earth and stone scarp, a sloping bank rather than a vertical wall, and the degree of survival varies considerably around the circuit. Between the eastern and southern sides, the scarp still stands to between 0.8 and 1.1 metres, while elsewhere it has eroded almost to ground level. A detail worth noting lies about 3.3 metres in from the southern edge, where a run of limestone uprights, roughly 4.2 metres long and only about 25 centimetres high, may represent the remnants of an original stone facing to the bank. Further boulders are scattered around the perimeter between east and southeast. The interior is not flat; it rises toward the centre, a feature sometimes associated with the accumulated debris of long occupation. The site was recorded on Ordnance Survey six-inch maps in both 1840 and 1916, and was classified as an earthwork in the Record of Monuments and Places in 1996, though it had likely been a feature of the local landscape for well over a thousand years before either survey bothered to note it down. A field boundary running roughly west-northwest to east-southeast passes immediately to its southwest, suggesting the working landscape has long arranged itself around this older presence.