This coastal fortification occupies a naturally defended position, connected to the mainland by a narrow natural causeway measuring just 2.4 metres wide. Such a restricted approach would have made the site easily defensible, requiring attackers to advance in single file whilst exposed to defenders positioned above.

The promontory's western side features an earthen bank rising to 0.75 metres in height, providing an additional layer of defence beyond the natural advantages of the site. This earthwork would have served both as a physical barrier and as an elevated position from which to observe approaching threats along the coastline. Within the fort's interior lies a roughly triangular platform extending approximately 14.8 metres from north to south, likely serving as the main area for structures or activities within the fortified space.

Like many of Ireland's coastal promontory forts, this site represents a type of fortification that made clever use of natural topography. Dating potentially from the Iron Age through to the early medieval period, these forts served various purposes; from defensive strongholds and centres of local power to places of refuge during times of conflict. The Carthage fort remains as a tangible link to the communities who once controlled and defended this stretch of Donegal's rugged coastline.