In a field in County Kildare, there is nothing to see. No earthwork, no wall, no visible outline on the ground. And yet, captured in aerial photography, the soil itself gives away the presence of something old: a rectilinear enclosure, oblong in shape, pressed faintly into the landscape as a cropmark.

Cropmarks appear when buried features, such as the filled-in ditch of a former enclosure, affect the growth of crops or grass above them. A fosse, which is simply a ditch dug to define or defend a boundary, retains moisture differently from the surrounding soil, causing the vegetation overhead to grow taller or denser, or to ripen at a different rate. Seen from the air, these subtle variations in colour and texture trace out the ghost of a structure that may otherwise have left no surface trace at all. It was an Ordnance Survey Ireland orthophoto taken in 2000 that recorded this particular enclosure at Quarry, revealing an outline that ground-level observation would almost certainly miss entirely.