The 29-metre enclosure at Annaghbeg is defined by an earthen scarp and bank with an external fosse, a drainage ditch running around its outer edge, and mature trees spaced at regular intervals both along the bank and within the interior. That orderly planting is the crux of the puzzle. When the first edition of the Ordnance Survey six-inch map was produced in the nineteenth century, the feature was recorded simply as a circular tree-planted enclosure, which suggests that whoever was looking at it then saw something deliberate and ornamental rather than ancient and defensive.

The question of what it actually represents has not been settled. A ringfort, known in Irish as a rath, is a type of enclosed farmstead typical of early medieval Ireland, usually defined by one or more earthen banks and ditches and used as a protected residence for a farming family. The Annaghbeg enclosure fits that basic description reasonably well, and limestone blocks visible on the outer face of the southern scarp may be the remnant of a stone revetment, a facing used to stabilise and strengthen an earthen bank, which would be consistent with a more substantial construction. On the other hand, the geometric regularity of the tree planting points towards a later landscape feature, perhaps a tree ring, the kind of circular plantation that landowners sometimes created in the eighteenth or nineteenth century as an ornamental or practical shelter feature. The fact that another ringfort sits only 350 metres to the north-north-east complicates things further; it raises the possibility that the Annaghbeg enclosure began as one thing and was later adapted or embellished into something else entirely.