That is not a paradox so much as a quiet historical fact: Tobar Caíllín, the well of Saint Caillin, was once a recognised sacred site on this small island, and now there is nothing to see at all. No stone surround, no seeping water, no votive offerings left by recent visitors. The ground above it gives no indication that anything was ever there.

Holy wells in Ireland were typically freshwater springs venerated for their association with a local saint, often visited on a saint's feast day in a ritual known as a pattern. Tobar Caíllín was one such site, lying some twenty metres to the east-north-east of a small oratory at the eastern end of the island. The antiquarian Roderic O'Flaherty recorded it in 1684, a note later republished by James Hardiman in 1846, which gives the well a documented history stretching back at least three and a half centuries. It appeared on the first edition of the Ordnance Survey six-inch map, the great mid-nineteenth-century survey that fixed so many Irish place names and features in cartographic form. But by the time the second edition was produced in 1899, the well had gone. The mapmakers noted only "Site of", that blunt cartographic shorthand for something that had ceased to exist. What destroyed it is not recorded.