This is a rath, the Irish term for a ringfort, the kind of enclosed farmstead that was built across Ireland in their thousands during the early medieval period, roughly between the fifth and twelfth centuries. Most people pass them without a second glance, if they notice them at all. This one at Glannaheera is small, with an internal diameter of around 16.7 metres, and what survives tells a story partly about how it was built and partly about how time and land use have worked against it.

The enclosing bank is univallate, meaning it consists of a single earthen rampart rather than the multiple concentric banks found at more elaborate sites. The way that bank has survived is telling. On the uphill side, facing NNW, it still stands 1.7 metres high on the outside, which would have made it a meaningful barrier. On the downslope side to the SW, the exterior height drops to just one metre and the interior face is barely visible at ten centimetres. A stretch of over ten metres along the ESE has been levelled altogether, likely cleared at some point for agricultural use. A small stream runs just outside the northern part of the bank, flowing south-east down the hillside. A gap of roughly 2.1 metres on the western side may preserve the position of the original entrance, a detail that matters because original entrances are not always easy to identify once a structure has been partially demolished. The topographical logic of the site is readable even now: the bank was built highest where the slope offered least natural defence, and the enclosure was positioned to command a view down the valley of the Emlagh river. The site was recorded by J. Cuppage in the Dingle Peninsula Archaeological Survey, published in 1986.