In a low-lying field near Killag in County Wexford, a ringfort betrays its presence not through any upstanding earthwork, but through the subtle differential growth of crops above buried features below. This kind of cropmark forms when buried ditches retain moisture differently from the surrounding soil, causing the vegetation above them to grow at a slightly different rate, a difference invisible to a person standing in the field but legible from altitude, particularly during a dry summer.

What the aerial photographs reveal is a roughly circular enclosure with an internal diameter of around 25 metres, defined by two concentric ditch features, known as fosses, that bring the overall external diameter to approximately 40 metres. A ringfort of this type, sometimes called a rath, was typically a farmstead enclosed by one or more earthen banks and ditches, and was the most common form of rural settlement in early medieval Ireland, broadly from the fifth to the twelfth century. The double-fosse arrangement here suggests a site of some elaboration, though without excavation it is impossible to say more about the people who built or used it. The surrounding landscape at Killag is notably level and low-lying, which both allowed the site to be constructed with relative ease and helps explain why so little survives above the surface today; centuries of agriculture on flat, workable ground tend to reduce earthworks to near nothing.