This one announces itself through almost nothing at all. At Cloonkerry in County Mayo, a rectangular outline roughly twenty metres east to west and twelve metres north to south is faintly discernible from aerial imagery, sitting in the north-west quadrant of a larger, levelled enclosure. On the ground, there is no visible trace whatsoever. What you are looking at, if you can be said to be looking at anything, is the ghost of a building that survives only as a subtle differential in the soil, legible to a satellite but invisible to a person standing on top of it.

The feature sits within a larger enclosure, itself now levelled, meaning the earthworks that once defined the boundary of this place have been reduced to the same flat agricultural surface as everything around them. Aerial and satellite photography can sometimes recover what ground-level survey cannot, because differences in soil compaction, moisture retention, and crop growth reveal themselves from above in ways that remain imperceptible at eye level. In this case, Google Earth imagery from November 2016 captured the faint rectangular outline well enough to suggest the presence of a former building, though its date, function, and relationship to the enclosure it once occupied remain uncertain.