The enclosure is roughly circular, measuring 31 metres north to south and 35 metres east to west, and the bank that surrounds it tells a more varied story than a simple loop of earth might suggest. Along the south-east to west arc it rises to around 1.5 metres; on the western to north-north-western stretch it drops to a scarp of 1.2 metres with a slight internal lip; and along the north-north-west to south-east section the bank stands about a metre in height on the interior. A gap of two metres in the bank to the south-east most likely marks the original entrance.

This is a rath, the Irish term for a ringfort, a type of enclosed farmstead that was the standard unit of rural settlement in early medieval Ireland, broadly from around the fifth to the twelfth centuries. Thousands survive across the country in various states of preservation, but each one carries its own particular proportions and quirks of construction. The variation in the Garranure bank, shifting between a built-up earthen wall and a cut scarp depending on where you are standing, suggests the builders worked with the natural lie of the ground rather than imposing a uniform design on it. The slight internal lip on the western arc may have helped retain a palisade or supported a walkway, though without excavation such details remain a matter of inference.