No one has found it. No trace of it breaks the surface. The rath at Corralea sits on a hill summit in undulating grassland in north County Galway, well-preserved and quietly imposing, and whatever the ground beneath it conceals, it has so far kept its secret.

The site is a rath, the most common type of early medieval enclosure in Ireland, typically consisting of a circular earthen bank enclosing a domestic space used by a farming family of some status, roughly between the fifth and twelfth centuries. This one is almost perfectly circular, measuring 42 metres north to south and 41 metres east to west, and is defined not by one bank but two, with a fosse, meaning a ditch, cut between them. A double-banked arrangement like this generally indicates a site of greater than ordinary importance. The entrance is well-defined at the north-west, and a later field wall has been built over the outer bank on the northern side, the kind of casual repurposing that happened across the Irish countryside once the original function of such earthworks had been forgotten. In the interior there is a conjoined burial ground, a feature that points to the site having accumulated meaning over a long stretch of time, with the enclosure outlasting its original inhabitants and taking on a different kind of significance for later communities. Then there is the tradition of the tunnel. A souterrain, which is an underground stone-lined passage often associated with ringforts and used for storage or refuge, would not be unusual in a site like this. But the particular detail of an iron gate lends the story a more dramatic flavour, and no archaeological investigation has yet confirmed anything beneath the surface.