Though it no longer exists, this ancient fortification was carefully documented on all editions of the Ordnance Survey 6-inch maps, where it appeared as a single-ringed fort. The site occupied an advantageous position on good, flat land that sloped gently northward towards Lough Swilly, offering its inhabitants strategic views across the surrounding countryside.

Ringforts like this one were amongst the most common archaeological features in medieval Ireland, typically dating from the early medieval period between 500 and 1200 AD. These circular enclosures, defined by earthen banks and ditches, served as defended farmsteads for prosperous farming families. The single ring at Castlecooly suggests it was likely a more modest settlement compared to the multi-ringed forts of wealthier landowners, though its prime location near the lough would have provided access to both agricultural land and water resources.

Today, no visible trace remains of this once-significant structure; the land has been transformed by centuries of agricultural use and development. The fort’s existence is preserved only in historical records and maps, serving as a reminder of the thousands of similar sites that once dotted the Irish landscape. Many of these ancient settlements have been lost to time, ploughing, and modernisation, making the archaeological surveys that documented them invaluable resources for understanding Ireland’s rich medieval heritage.