A circular enclosure roughly thirty metres in diameter lies hidden beneath the surface, its presence betrayed only from the air, where the outline of an ancient fosse, a defensive or boundary ditch dug into the earth, shows up as a cropmark during dry conditions when buried features cause the vegetation above them to grow differently from the surrounding soil.

Cropmarks of this kind are typically revealed through aerial photography taken during summer droughts, when differences in soil moisture and depth cause crops to ripen at varying rates, tracing the shapes of whatever lies beneath. The enclosure at Grange was identified through exactly this method, captured in aerial photographs that show the circular form with reasonable clarity. Circular enclosures defined by a fosse are a broad and ancient category of monument in Ireland, encompassing everything from prehistoric ritual sites to early medieval ringforts, which were the farmsteads of wealthy families in the period roughly between 500 and 1200 AD. Without excavation, it is not possible to say which period this particular enclosure belongs to, or what purpose it served. What the aerial record confirms is its shape, its approximate scale, and the fact that the ditch defining it was substantial enough to leave a legible impression in the ground nearly a millennium or more after it was dug.