The enclosure, possibly D-shaped and approximately 60 metres in diameter, was defined by a fosse, the term for a ditch or trench used to demarcate an enclosed area, and was visible only as a cropmark, a pattern in growing vegetation that reveals buried or disturbed soil beneath. Cropmarks of this kind are often the sole surviving evidence of early medieval settlement enclosures, farmsteads, or ritual sites, and they appear only under the right combination of dry weather and low-growing crops.

The aerial photographs taken on 10 July 1973 show not only this enclosure but a second circular one immediately to the north-west, the two possibly conjoined into a paired or double enclosure arrangement. A third enclosure lies roughly 50 metres to the south-east, suggesting this ridge was once a focus of some sustained human activity. The site sits on elevated ground with broad views across rolling grassland, which is consistent with the kinds of positions chosen for enclosed settlements throughout early medieval Ireland. What makes the Dunmore example particularly sobering is its subsequent history. Satellite imagery from 2005 and 2010 showed that the field had been quarried, with both the main enclosure and its north-western companion badly damaged and perhaps largely removed. By 2019, the quarry appeared to have been filled in and the land returned to agricultural use, leaving little or nothing of the original earthworks above or below the surface.