The one at Creenagh, Co. Leitrim, is the latter. Sitting on top of a low rise in what was, at least in the early 1990s, open pasture, it left no visible trace at ground level when examined in 1991, and yet from the air its shape is unmistakable.

Aerial photography reveals a bivallate ringfort, meaning one defined by two concentric circuits rather than the single bank-and-ditch arrangement more commonly encountered. Here, a wide inner fosse, that is a defensive ditch dug around the enclosed area, is accompanied by a narrower outer one, together producing a roughly circular enclosure with an internal diameter of around 50 metres and an external diameter of approximately 80 metres from north to south. Ringforts of this type are generally associated with early medieval settlement in Ireland, typically dating to somewhere between the fifth and twelfth centuries, and were the farmsteads or residences of families of some local standing. The bivallate form, with its additional circuit of earthworks, is often taken to indicate higher social status or greater defensive concern, though the earthworks here have been so thoroughly reduced by centuries of ploughing and grazing that none of this is legible on the ground. By 2013, satellite imagery showed the surrounding area still unplanted within a forestry block, meaning the site itself had at least avoided the further compression that tree roots and drainage works can cause.