A rath is an early medieval enclosure, typically circular, formed by one or more earthen banks, and this one in Doire Mhór Thiar has been reduced to a single eroded bank, gapped and spread in places, reaching no more than 1.1 metres at its best-preserved points. That modest profile, though, belies a site that contained a souterrain, a subterranean stone-lined passage used in early medieval Ireland for storage or concealment, whose full extent was described to surveyors not by any excavation but by the landowner from memory. The passage, they reported, ended in a cruciform chamber, a cross-shaped arrangement that would be an unusual feature in such a structure anywhere in Ireland.

The rath measures roughly 26.9 metres north to south and 25 metres east to west internally. Its south-facing entrance, just one metre wide, is lined on each side by a single course of stones, a small but deliberate detail that survives where much else has not. Inside, the outline of a circular hut about four metres in diameter can be traced slightly south-west of centre, its north-east arc marked by low stone heaps and its south-west side by a short surviving run of walling. Outside the enclosing bank, to the west-north-west, a spread of raised stones preserves traces of two further possible hut sites: one a rectangular hollow defined by low stones, the other suggested by a crescent-shaped stony bank. The souterrain itself is now visible only as a slight hollow and a few large surface slabs, though a blocked aperture in the western bank of the ringfort is likely connected to it. A bullaun stone, a boulder with one or more artificially ground hollows whose purpose may have been ritual or practical, has also been recorded at the site, noted by O'Connell as early as 1939. The archaeological description of the site was first published by J. Cuppage in the 1986 Corca Dhuibhne survey of the Dingle Peninsula.