In the stony pasture of Rockfield in County Mayo, an area of undulating ground broken by limestone outcrops, there was once a field wall whose entire existence now survives in a single aerial photograph. The wall followed a zig-zag course across rough ground, skirting outcrops and shifting with the natural contours of the land. It was removed during reclamation works, and nothing remains at ground level.

What the aerial photograph captured before the wall's removal was a boundary that seemed to work with the landscape rather than impose upon it. The zig-zag alignment, rather than reflecting carelessness or piecemeal construction, most likely reflects a practical response to the irregular limestone outcrops that characterise this part of Mayo. Field walls of this kind are often far older than they appear, with origins that can reach back into the medieval or even early medieval period, the line of a boundary sometimes persisting in the land long after the original builders are forgotten. Close to the south of this wall, a possible enclosure has also been recorded, suggesting the wall may have formed part of a wider pattern of land use and division in this small area.

The photograph that preserves the wall is an Ordnance Survey aerial image, and it remains the sole documentary evidence for a feature that is otherwise entirely gone. There is a particular quality to a place whose history is held only in an archive image, where the ground itself offers no confirmation. Rockfield, in this respect, is less a site to visit than a reminder of how much of the Irish landscape has been quietly erased before it could be fully understood.