This is a rath, the earthen variety of ringfort, and the form it takes here has changed remarkably little since it was first constructed, most likely during the early medieval period, roughly between the fifth and twelfth centuries. Ringforts of this type served as enclosed farmsteads, the bank and its accompanying external fosse (a defensive ditch) marking out a protected domestic space for a farming family and their animals.

The earthwork at Dreenagh measures approximately 28 metres from north-north-east to south-south-west and just over 27 metres east to west, making it a fairly standard example of the type in terms of scale. The external fosse reaches a depth of around 1.5 metres and has a flat bottom, though it has silted and slipped somewhat on the southern side over the centuries. A causeway outside the entrance, which faces east and is just 1.6 metres wide, would once have provided a controlled crossing point over the ditch, a detail that speaks to the practical, everyday security concerns of its original occupants rather than any grand military ambition. The bank itself has long since been colonised by deciduous trees, giving the whole enclosure the appearance of a low, wooded ring when viewed from a distance.

The interior is partially overgrown, and the site sits within working pasture, which is a common situation for ringforts across Ireland. Many survive precisely because generations of farmers recognised something in these circular earthworks worth leaving alone, whether from practical caution or older instinct. The entrance to the east is still traceable, and the overall form of the enclosure remains coherent enough that the original layout, bank, fosse, causeway, and gap, can be read clearly on the ground.