Others are so faint that they exist, in any practical sense, only from the air. At Boolies in County Meath, a circular enclosure roughly thirty metres in diameter lies on a gentle south-east-facing slope, its outline so slight that it cannot be made out at ground level at all. The only way to see it is through satellite imagery.

The enclosure is defined by a fosse, a shallow ditch that would originally have marked the boundary of the enclosed area, though centuries of agriculture and weathering have reduced it to the merest depression beneath the grass. It was first reported by Jean Charles Caillére, and the feature became visible to researchers through Google Earth imagery captured in January 2020. Circular enclosures of this kind are common across the Irish landscape and range in date and function from prehistoric settlements to early medieval ringforts, but without excavation or closer survey it is impossible to say more about what this particular example represents. What is notable here is less the site itself than the manner of its discovery: a fragment of the past recovered not by fieldwork but by scrutinising a satellite image on a screen.