It would pass entirely unnoticed to anyone walking the ground, yet from above, in the right conditions, it reveals itself as a cropmark, a ghostly trace left in ripening grain where buried features alter how plants grow and how they colour as summer advances.

Cropmarks form when buried ditches or walls affect the soil's moisture and nutrients directly above them. Ditches retain more water, encouraging lusher, darker growth; buried stone does the opposite, stressing the crop above it into early yellowing. Seen from sufficient height in dry summer conditions, these variations produce outlines of structures that vanished from the surface long ago. The enclosure at Redbog was identified in exactly this way, spotted on Google Earth imagery captured on 14 July 2018 by Simon Dowling, who reported it for the record. What the image shows is an oval roughly 30 metres along its north-east to south-west axis and about 17 metres across, orientated in the tillage like a faint bruise in the crop. Oval enclosures of this kind are scattered across the Irish countryside and can range in date from prehistoric to early medieval; without excavation, the age and function of this one remain open questions.