At Treanlaur in County Galway, a hilltop enclosure contains, or once contained, the traces of a souterrain, one of those long, stone-lined underground passages or chambers that early medieval communities used for storage and, occasionally, refuge. The catch is that no visible surface trace of it remains today, which puts it in a category of archaeology defined more by rumour and inference than by anything a visitor could actually see or touch.

The detail comes from a 1912 account by a writer named Holt, who recorded not that a souterrain existed, but that it was said there were traces of one within the enclosure. That single degree of remove is telling. Even in 1912, the feature was already more tradition than physical fact, something people pointed to rather than stood inside. The enclosure itself sits on high ground, which was a common choice for defended or ceremonial sites in early medieval Ireland, offering visibility across the surrounding landscape. Whether the souterrain, if it existed, served the community associated with that enclosure, or belongs to an earlier or later phase of activity on the hill, is not something the surviving record can answer.