Though it has since been removed from modern Ordnance Survey maps, this defensive structure was documented on the first and second editions of the OS 6-inch maps, marking its place in the archaeological record of Ireland’s northwest coast.

The fort occupied a flat-topped area roughly 20 metres across, its circular outline barely discernible even when it was first recorded. The site’s strategic position made excellent use of the natural topography; the ridge provided good grazing land whilst offering defensive advantages, with the ground dropping away sharply on both the eastern and western flanks into wetland below. This combination of elevated position and difficult approaches would have made it an ideal location for a fortified settlement, offering both security and sustenance to its inhabitants.

Today, visitors to Duibhleann Mór will find little physical evidence of the fort itself, but the landscape tells its own story. The narrow ridge still projects into the waters of Mulroy Bay, and the contrast between the firm grazing ground atop the ridge and the boggy terrain below remains as pronounced as it would have been centuries ago. This unclassified ringfort represents just one of many such structures scattered across County Donegal, each a testament to the complex patterns of settlement and defence that characterised medieval Irish society.