The earthen platform rises between 1.5 and 2.5 metres above the surrounding countryside, forming a roughly circular enclosure measuring approximately 20 metres from east-northeast to west-southwest and 18 metres from north-northwest to south-southeast. A defensive bank, reaching heights of up to 1.5 metres, encircles the perimeter with two gaps; one original 2-metre entrance to the east and another modern breach to the south.

The site’s strategic positioning takes full advantage of the natural topography, with steep drops to both east and west providing additional defence. Today, the ringfort sits in well-maintained pasture land, though some modern disturbance is evident within the interior. These earthworks, known locally as raths, were typically constructed between the early medieval period and the 17th century as fortified farmsteads for prosperous families.

The archaeological record for this site comes from the comprehensive Archaeological Survey of County Donegal, compiled by Brian Lacey and colleagues in 1983. This extensive survey documented field antiquities across the county spanning from the Mesolithic period through to the 17th century, providing invaluable insights into Donegal’s rich archaeological heritage. The ringfort at Aghadreenan represents just one of hundreds of similar structures that once dotted the Irish countryside, serving as both defensive positions and symbols of social status in early Irish society.