That uncertainty is, in its own way, the whole story.

When the antiquarian Rolleston visited in 1900 and recorded his observations, he could trace the remains of a stone wall separating the clifftop headland from the interior of the island, a layout consistent with what are known as coastal promontory forts, a type of enclosure in which a natural sea-cliff does most of the defensive work and a constructed barrier closes off the landward side. He compared what he saw to similar structures on the Aran Islands. But Rolleston could not bring himself to commit: the wall, he felt, might equally be the remnant of a much more mundane modern fence. Thomas Johnson Westropp, who compiled a more systematic treatment of such sites in 1912, mentioned Caher Island in passing but pointedly left it off his main list, suggesting he shared something of Rolleston's hesitation. The site has not been independently visited or surveyed since, leaving the question precisely where those two men left it, unresolved and quietly suspended somewhere between prehistoric enclosure and agricultural boundary.