No earthwork rises above the field, no ditch catches the eye, no bank of soil marks out where people once lived and farmed. What betrays this site is something altogether more ghostly: a cropmark, visible only from the air, tracing the outline of a circular enclosure roughly 35 metres across on the crest of a west-facing slope.

Cropmarks form when buried features, such as the filled-in ditch of an ancient enclosure, affect how plants grow above them. Soil that has accumulated in a ditch tends to hold more moisture, producing a slightly lusher strip of crop that, from altitude, reads as a darker line against the surrounding field. In this case, an aerial photograph captured just such a pattern, a single curved fosse, meaning a ditch, completing a circle and preserving in the landscape the faint memory of a rath. Raths, also known as ringforts, were the most common form of rural settlement in early medieval Ireland, typically enclosing a farmstead with one or more earthen banks and ditches. Thousands survive across the country in varying states of preservation; this one in Kilhile has essentially vanished at surface level, surviving only as a signal in the soil.