What was once an irregular, roughly oval earthwork, measuring approximately 48 metres north to south and 62 metres east to west, has been levelled entirely by agricultural activity. Its outline survives as a cropmark, the ghostly trace left when buried features such as a fosse (a defensive ditch) cause crops above them to grow at a slightly different rate, revealing the shape of the original structure when seen from altitude. A 1995 aerial photograph captured exactly this effect, preserving a plan of something that would otherwise be lost entirely.

The enclosure at Coolgrange was not always invisible. Both the first edition Ordnance Survey six-inch map of 1839 and its 1900 revision recorded it clearly as a standing earthwork on a hillslope. Its position is significant. Directly across the valley on Freestone Hill sits a hillfort and a cairn, the kind of pairing that suggests this landscape was intensively used and perhaps ceremonially important over a long period. The enclosure at Coolgrange would have faced that hill, and a second enclosure has since been identified as a cropmark immediately to the north, suggesting this was not an isolated feature but part of a broader pattern of occupation or activity in the area. The precise date and function of the Coolgrange enclosure remain unconfirmed, but its scale and form are consistent with the enclosed settlements found across Ireland from the prehistoric period onwards.