In a pasture in County Kilkenny, what looks like ordinary farmland conceals the outline of a circular enclosure roughly twenty metres across, legible only from the air as a cropmark, the faint but readable signature of a buried fosse, or defensive ditch, pressed into the soil beneath the grass. Cropmarks form when buried features such as ditches, walls, or pits affect the moisture and nutrient content of the soil above them, causing the crops or grass growing at the surface to ripen at slightly different rates, producing patterns that become visible from altitude, particularly during dry summers when the variation in the vegetation is most pronounced.

The enclosure at Annamult was identified from an aerial photograph taken on 16 July 1971, part of the Cambridge University Collection of Aerial Photography, a body of work that has been quietly instrumental in locating buried and otherwise invisible archaeological sites across Ireland and Britain. On the same photograph, a second enclosure of similar type appears roughly 130 metres to the south-east, and the cropmark of an older field boundary can be seen cutting across the monument in a roughly east-west direction. The relationship between these features is not fully known, but the overlapping traces suggest a landscape with more than one phase of use, layers of activity in the same ground that have never been excavated or formally dated. Curvilinear enclosures of this general type are widespread in Ireland and are often associated with early medieval settlement, though without excavation that remains a general observation rather than a specific claim about this site.