Marked on the 1945 edition of the Ordnance Survey six-inch map as a circular enclosure roughly 44 metres in diameter, it had already been effectively erased from the landscape by the time anyone went to look at it properly. When an inspector visited in April 1984, the site had been levelled. What remained was barely a whisper: a slight change in vegetation colour tracing an arc from the north, around through the east, and down to the south, hinting at where the fosse once ran. A fosse, in this context, is the ditch that would originally have defined and defended the enclosure's perimeter, the kind of earthwork feature common to ringforts and similar enclosed settlements throughout Ireland.

What makes Coolbaun quietly remarkable is the gap between what the eye can see on the ground and what becomes legible from above. Aerial and satellite photography, particularly DigitalGlobe imagery from 2016, reveals the enclosure's complete outline with considerable clarity, the kind of visibility that comes when buried archaeology influences soil moisture and nutrient levels in ways that show up in differential grass growth. The western-facing slope in grassland, which might look entirely unremarkable to a walker crossing it, holds the ghost of a structure that the OS surveyors of the mid-twentieth century could still observe as a physical feature. Somewhere between 1945 and 1984, it was gone.