In the summer of 1971, a Cambridge University aerial photography mission captured what the soil had been quietly preserving: a roughly square enclosure, approximately 30 to 35 metres across in both directions, showing up as the cropmark of a fosse. A fosse is a ditch, typically dug as a boundary or defensive feature around an enclosed space, and when crops grow above its filled-in remnants they often ripen at a slightly different rate to the surrounding soil, producing a tell-tale line of colour visible from altitude but not from the ground.

What the photograph revealed was not a simple shape. Running across the interior of the square enclosure is the cropmark of a field boundary oriented roughly east-north-east to west-south-west, dividing the space within. More striking still is the spatial relationship between this square enclosure and its neighbour: it sits directly against the south-eastern sector of a separate, roughly circular enclosure nearby. The pairing of circular and square or rectilinear enclosures is known elsewhere in the Irish archaeological record, though what specific function or period this Annamult example belongs to remains unresolved from the aerial evidence alone. Circular enclosures in Ireland are often associated with early medieval settlement, while rectilinear forms can suggest a range of uses and periods, from prehistoric to early historic.