The enclosure measures roughly 25 metres in diameter and is defined by an earthen bank, the kind of boundary that would once have enclosed a family's house, animals, and daily life. It is easy to miss, particularly given that the site is described as heavily overgrown, and that farmland has a way of slowly absorbing the past into its working rhythms.

What lifts this particular rath above the merely typical is the presence of a souterrain in its interior. A souterrain is an underground stone-lined passage or chamber, constructed during the early medieval period and associated with ringfort settlements across Ireland. Their precise purpose is still debated, but they are generally thought to have served for storage, as refuges, or both. Thousands of ringforts survive across the Irish landscape, most dating from roughly the sixth to the tenth century, and they represent the most common form of rural settlement from that period. The earthen bank at Derrygool is the rath type, as distinct from stone-built cashels, and its modest scale is fairly representative of the single-family farmsteads that once dotted the Cork countryside.