The ringfort at Caltraghcreen, on a south-east-facing hillside in County Galway, has long been known in the area as King's Fort, a name that implies a status above the ordinary. What survives in the grassland there is unusually well-defined: a circular rath measuring some 34.5 metres in diameter, enclosed not by the single bank-and-fosse arrangement typical of many such sites, but by two banks with two intervening fosses, and traces of what may be a third fosse visible along the northern side.

Raths, the earthen ringforts that dot the Irish countryside by the tens of thousands, were generally built during the early medieval period, roughly the fifth to the twelfth centuries, and served as enclosed farmsteads for families of some local standing. The more elaborate the earthworks, the higher the social rank that was likely associated with the occupant, which lends the King's Fort name a certain logic. Multiple banks and ditches were a mark of prestige, and this example, with its layered defences, would have signalled something considerable to anyone approaching across the hillside. Adding to the sense of a more complex site is the presence of a probable souterrain in the interior, a souterrain being an underground stone-lined passage or chamber, typically used in early medieval Ireland for storage or as a place of refuge.