The photograph, taken on 13 July of that year, revealed a cropmark, the faint but legible trace left when buried archaeology influences how crops grow above it, outlining what appears to be a roughly circular enclosure about 40 metres in diameter. Defined by a fosse, which is a defensive ditch dug around a settlement or ritual space, the enclosure also has a rectilinear annexe attached to it and a possible entrance oriented towards the southeast. None of this is visible to someone walking the field. It exists, for practical purposes, only from the air.

Cropmarks like this one are produced when buried ditches or banks alter the moisture and depth of soil above them, causing the crops to grow taller or shorter, greener or more parched, in patterns that mirror the buried features below. The Annamult enclosure belongs to a type found across Ireland, though its precise date and function remain unestablished from the available evidence. What adds a small layer of archaeological interest to the site is its proximity to a ring-barrow, a low circular earthwork typically associated with burial, located approximately 170 metres to the southwest. Whether the two features are related in date or purpose is an open question. A further complication, almost poignant in its mundanity, is that a modern field boundary runs north to south directly through the centre of the enclosure, and the cropmark is not visible on the western side of that boundary, meaning the record assembled from the 1989 photograph is necessarily incomplete. Part of the enclosure may be there; the evidence simply does not reach across the fence line.