Set on a west-facing slope above a sharp drop down to bogland, with the Foherish River immediately to its east, the site presented an awkward engineering problem, and the solution is still legible in the ground today.

A ringfort, or rath, is a roughly circular enclosure defined by one or more earthen banks, typically built during the early medieval period in Ireland as a farmstead or place of settlement. At Gortavranner, the enclosure measures about 40 metres east to west and 39 metres north to south, enclosed by an earthen bank that rises to 2.4 metres, with an external fosse, a defensive ditch, running from the south-west round to the south-south-east. The entrance, facing south-east, is 3.6 metres wide and is approached by a causeway across the ditch. The most telling detail is on the western side: because the ground falls away so sharply there, the bank was raised to 4.4 metres on that side to maintain a consistent enclosure. The interior has taken on a saucer-like shape over time, a result of the inner face of the bank eroding inward across the centuries. The combination of the natural topography and the compensating bank height gives the structure an asymmetry that is unusual and worth examining closely once you are standing inside it.