Two separate flights of stone steps rise up the inner face of this cashel, a type of circular stone ringfort built without mortar, and they do so in entirely different ways. One set sits within a recessed straightforward climb; the other projects outward from the wall-face in what has been called a sideways flight, its steps cantilevered out rather than tucked in, possibly leading to a terrace that no longer survives in any obvious form. Interior steps of this kind are considered a characteristic feature of the Western Stone Forts of the Atlantic seaboard, placing Caherminnaun in distinguished company, if not the most famous of it.

The antiquarian Thomas Johnson Westropp visited and documented the site in 1915, and his description remains pointed. He noted that the dressed masonry was unusual in following long, sloping courses that ran into wedges between adjoining layers, neither the horizontal nor the polygonal arrangement typical of comparable structures. The entrance gateway, now blocked by rubble, was also singular: four small pillar stones, one at each corner angle, defined its opening, though the lintels had already been thrown down by Westropp's time. The wall itself is double-faced, built from large limestone blocks roughly 0.8 metres long, and the cashel interior measures nearly 29 metres north to south. The structure sits in low-lying pastureland within a wider multiperiod field system, with an associated enclosure about 70 metres to the east and a holy well some 136 metres to the north-east. It appears on the Ordnance Survey six-inch maps of both 1842 and 1920, labelled in the latter as Caherminnaun, and on Tim Robinson's celebrated 1977 map of the Burren as Cathair Mhionnán.

Both flights of steps survive, though the southern flight now has only three of its original four steps remaining. The original entrance at the south-east is blocked, and a modern gap has been cut into the northern side of the wall, damaging it in the process. Inside, a later collapsed field wall crosses the interior, and a rectangular stone structure built against the inner wall-face is likely the sheepfold recorded on the Ordnance Survey twenty-five inch plan, a reminder that the cashel's enclosing walls went on being useful long after their original purpose was forgotten.