The one at Carhan is a univallate rath, meaning it has a single enclosing bank rather than the multiple concentric rings that mark higher-status sites, but what it lacks in grandeur it compensates for in the density of activity preserved within its earthen circuit. The bank still stands 1.4 metres above the exterior ground, with a basal width of 3.5 metres, and a causeway at the western side leads across the outer fosse, a shallow defensive ditch, to a 3-metre entrance gap that almost certainly reflects the original way in.

Inside the enclosure, the archaeology accumulates in layers. Two curving sections of drystone wall near the eastern interior suggest a conjoined hut structure, while arcs of masonry to the north and south represent further huts, one with an internal diameter of roughly 3 metres and the other around 5.5 metres. The wall-faces that survive are horizontally coursed and preserved to about 30 centimetres in height, which is modest but enough to trace the outlines of domestic life. Most strikingly, the centre of the rath contains the remains of a souterrain, an underground stone-lined passage typically associated with storage or refuge, marked now by a 7.5-metre depression running north to south. Only a single lintel stone remains in place, and the accessible portion of the passage runs to just under 1.7 metres in length. When Donaldson examined the site in 1956, he noted that the interior had been disturbed in the 1950s and that traces of ash and charcoal were visible beneath the sod, a reminder that digging of any kind can erase what centuries of vegetation had quietly kept. Two quern-stones used for hand-grinding grain, now sitting in an adjacent farmyard, are said locally to have originated here, which, if true, adds one more thread to a picture of a self-contained agricultural household going about its work inside these banks sometime in the early medieval period.