This circular enclosure, measuring approximately 20 metres in diameter, has been reduced by time to a low, grassy platform rising just half a metre above the surrounding fields. The site appears to have originally formed a semi-circle, with its northern edge marked by a dramatic seven-metre drop. Today, a modern stone field wall runs east to west along this northern boundary, whilst traces of the original perimeter bank, now only 20 centimetres high, can still be detected amongst the stones and grass.

The exact nature of this ringfort remains somewhat uncertain; whilst it could have been an earthen structure, the stony composition of the platform suggests it was more likely a cashel, a stone-built fortification typical of early medieval Ireland. These structures served as defended homesteads for farming families between roughly 500 and 1200 AD, providing protection for both people and livestock. The strategic positioning of An Dún Mór is typical of such sites, situated on level ground with a gentle rise providing oversight from the west, whilst to the east, the land slopes gradually down towards the Ray river.

Despite its ruined state, the site offers valuable insights into the settlement patterns of ancient Donegal. The Archaeological Survey of County Donegal, compiled in 1983 by Brian Lacey and his team, documented this and hundreds of other monuments across the county, preserving knowledge of these fragile remains for future generations. Though easily overlooked by the casual observer, An Dún Mór represents just one of thousands of ringforts that once dotted the Irish landscape, each telling a story of the families who lived, worked, and defended their small piece of land in Ireland's distant past.