The first edition Ordnance Survey six-inch map, surveyed in 1839, shows a clearly defined D-shaped enclosure, roughly 38 metres along its longer axis, with a flat straight side running northwest to southeast. Inside it sat a substantial rectangular building, about 15 metres long and 7 metres wide. By the time the revised OS map was produced in 1899, both enclosure and building had vanished from the cartographic record, replaced by a loosely drawn irregular area filled with the small symbols surveyors used for trees. Whatever the enclosure once was, it had become, at least in the eyes of the mapmakers, a plantation.

Enclosures of this type are a recurring feature of the Irish landscape, early medieval in character for the most part, typically defined by an earthen bank or a stone wall and used to demarcate a settlement, a farmstead, or sometimes a site with religious or ceremonial significance. What makes this one at Knockanaddoge quietly interesting is precisely the gap between its two appearances in the record. A site substantial enough to support a large internal building in 1839 had, within sixty years, been absorbed into a tree plantation, its boundaries dissolved. When the site was visited in 1987, the plantation was dense enough to be largely impenetrable, crossed by several deep drainage channels that further disturbed the ground. The enclosure itself may still lie beneath, obscured rather than gone. Local tradition, in any case, has not forgotten the place; there are fairy associations attached to this monument, the kind of folk memory that tends to survive longest around sites whose original purpose has become uncertain or strange.

The terrace position means the site would originally have commanded good views in all directions, a quality often deliberately chosen by whoever established such an enclosure. Whether anything of the earthwork is visible on the ground today, beneath the trees and the drainage works, is difficult to say from any distance.