It is well-preserved, stone-faced, and largely unbroken, except for a gap at the south-east that may mark where people once passed through.

This is a rath, the Irish term for a ringfort, the most common monument type in the Irish countryside. Ringforts were enclosed farmsteads, built and occupied mainly during the early medieval period, roughly between the fifth and twelfth centuries, though some examples are earlier. The enclosing bank was not primarily a military fortification but rather a boundary marker that defined a household's space, kept livestock in, and offered a degree of social as well as physical demarcation. They were typically the homes of farming families of some local standing. The Pollynoon example is defined by a stone-faced bank rather than a simple earthen one, which reflects the local building tradition of a region where stone is readily available. The ringfort sits on a slope looking out over a lake to the south, a position that combines practical advantages of drainage and visibility with the kind of outlook that early medieval farmers, like farmers in any period, would have valued.