The fort at Oughtdarra in County Clare follows that same logic, but the sea is nowhere near it. Instead, it occupies a high limestone headland in the Burren, using a sheer cliff face to the east and natural cliff edges to the south-west and west as its barriers, with a substantial stone wall drawn across the neck to the north-east. It is this inland application of a typically coastal design that makes it genuinely unusual, a quirk noted by the antiquarian Thomas Johnson Westropp, who described it in 1905 as 'the great inland promontory fort of Doonaunmore'. He also drew attention to what he called the 'farbreag', a detached rock pinnacle near the southern end, a natural oddity that only adds to the strangeness of the place.

The fort, marked as Dúnán Mór on Tim Robinson's 1977 map of the Burren, encloses a roughly rectangular area measuring approximately 176 metres on its long axis and around 90 metres across. The main defensive wall, which curves outwards across the headland's neck, reaches up to 5.4 metres wide and between 2.4 and 2.7 metres high at its most substantial point, with the outer face generally better preserved than the inner. The interior rises in a stepped fashion, sitting some 10 to 14 metres above the ground level outside the wall, giving the enclosed space an almost theatrical elevation. Westropp also recorded an internal terrace and what appeared to be one or two vertical joints on the wall's exterior, details consistent with phased construction or repair. He illustrated several hut sites along the inside of the north-east wall, though by the time a field inspection was carried out in 1998 most of these were no longer clearly identifiable on the ground. One hut site does remain traceable, abutting the interior of that wall. A slab wall extends northward from the promontory before turning north-west, where it connects, roughly 150 metres away, with a small field system that may itself be of considerable age. The whole complex sits within a broader ancient landscape of field systems, suggesting this was not simply a refuge but a place embedded in organised agricultural territory.