This one exists, for now at least, only as a pattern in a crop. At Ballyandrew in North Cork, what was once a rath, the Irish term for a roughly circular earthen enclosure used as a farmstead during the early medieval period, survives not as a visible mound or ditch but as a cropmark: a faint circular signature left in growing grain or grass where the buried remains of a bank and outer fosse alter the soil's moisture and nutrients enough to show up from the air.

The enclosure measures approximately twenty-five metres in diameter, and its existence was confirmed through aerial photography. Cropmarks of this kind form because buried features, whether a filled ditch or a collapsed bank, affect how plants grow directly above them. A former fosse, which is a defensive ditch dug around the outside of a rath, tends to retain more moisture than the surrounding subsoil, producing a slightly lusher, darker stripe of vegetation visible from altitude. The bank itself, compacted or spread across the interior over centuries, may suppress growth in a corresponding arc. Together these form the ghostly circular outline that the aerial photograph captured. Tens of thousands of raths once dotted the Irish countryside, representing the everyday settlements of farmers and their extended families between roughly the fifth and twelfth centuries, and a significant number survive only in this vestigial form.

There is little to direct a visitor to any particular spot on the ground. Without knowing the precise field location and the right conditions of crop growth and light, the enclosure would not be legible at eye level. Its life, for now, is an aerial one.