These fortifications, typically dating from the Iron Age through to the early medieval period, were strategically positioned on headlands and clifftops to take advantage of natural defences provided by steep drops to the sea on multiple sides. The Ardagh example follows this classic pattern, with earthworks and possibly stone ramparts cutting off the landward approach to create a secure enclosure.

Promontory forts like this one served multiple purposes for ancient communities. They functioned as defensive strongholds during times of conflict, centres for trade and craft production, and symbols of power for local chieftains. The coastal location would have provided excellent views for monitoring maritime traffic and potential threats, whilst also offering access to marine resources that supplemented the diet and economy of its inhabitants.