On a north-facing slope of a ridge in pastureland at Kilcaimin in County Galway, a rectangular enclosure once spread roughly 61 metres east to west and about 30 metres north to south. It had a slightly curving bank and an external fosse, which is a defensive ditch, running along its northern side, with scarps defining the eastern and western edges. Inside, a raised inner platform occupied the southern portion of the interior, merging into the hillside behind it. Today, none of this is visible at the surface.

The site was classified in 1952 by McCaffrey as an earthen fort, a broad category applied to enclosures of this kind, which in Ireland can date from the prehistoric period through to the early medieval and even later. The design here, with its internal platform and use of natural topography, suggests a site that made deliberate use of its position. Writing earlier, in 1912, Holt recorded a vague local tradition of a castle associated with the location, and remarked on the strategic quality of the ridge. A separate monument record exists for that putative castle nearby, suggesting the folk memory may have preserved at least a trace of genuine historical use. Whether the earthwork predated any castle structure, or whether the two were in some way related, is not something the available evidence settles.