At Roo in County Galway, a circular enclosure once occupied a prominent rise in pastureland, but nothing of it can be seen today. No bank, no ditch, no scatter of stone. The site exists now almost entirely as a classification in an old survey.

When the archaeologist McCaffrey catalogued the site in 1952, he measured it at roughly 35.7 metres in diameter and placed it in the category of earthen fort, the most common type of ringfort, a farmstead enclosure of the early medieval period typically defined by one or more earthen banks. But he was not entirely convinced by his own classification. He noted the possibility that it had originally been a stone fort with an earthen cover, meaning a cashel, the drystone-walled equivalent found widely across the west of Ireland, whose masonry had perhaps been quarried away or had slumped and spread over centuries until it was indistinguishable from ordinary soil. That uncertainty has never been resolved. Whatever the structure once was, the ground above it offers no answer.