On a south-facing slope at Knocknacreeva in County Galway, there was once a cashel, a type of stone-walled ringfort that would have enclosed a farmstead or small settlement during the early medieval period, roughly between the fifth and twelfth centuries. Today, no visible surface trace of it survives. The ground gives nothing away.

What we know comes from cartographic evidence rather than anything you could run your hand along. The site was named 'Caher' on the Ordnance Survey Fair Plan, an early working document produced during the great nineteenth-century mapping of Ireland, and it appeared on the first edition of the six-inch Ordnance Survey map as a circular enclosure approximately forty metres in diameter. That diameter is consistent with a modest but substantial cashel, the kind that would have housed a single family of some local standing. The name itself is telling: 'caher' derives from the Irish 'cathair', a term used specifically for stone-built ringforts, distinguishing them from the earthen-banked raths that are more common across much of the country. Someone, at some point, knew exactly what this place was and what it was called. That knowledge made it onto the maps. The structure itself did not survive long enough to make it into the present.