Excavations at the north entrance of the fort's middle enclosure revealed that the earliest occupation was not a building in any conventional sense, but a natural dip in the rock, measuring roughly three metres by just over a metre, which appears to have been deliberately used and perhaps slightly modified as a living area. No walls were erected around it, at least none that survived, yet the hollow's fill told its own story: animal bone, scattered limpet shell, charcoal, and five sherds of cooking pottery, the ordinary residue of daily life.

The excavations, focused on what archaeologists designated Cutting 9, identified two separate zones of activity on either side of the entrance passageway. To the east, the bedrock hollow was the primary feature, with a possible hearth located just to its south-east. As occupation continued, a paved pathway was laid to the west of that hearth, running north-west towards the hollow, suggesting the space was being organised more deliberately over time. A small fragment of double-faced walling, less than two metres long and only around twenty centimetres high, was also uncovered to the east of the hollow, running beneath the later wall terrace. To the west of the entrance, a separate paved surface marked another zone of early habitation, with charcoal staining, burnt animal bone, and three carefully placed limestone slabs pointing to a hearth. A radiocarbon date obtained from animal bone at this western zone places the activity firmly in the Bronze Age, somewhere between 1260 and 920 cal. BC. That means people were occupying this precise spot at least three thousand years ago, well before Dún Aonghasa took the monumental form visible today. The great enclosing walls came later; the hearth came first.