That proximity is not accidental. The site at Eden Island is a ringfort, or at least what remains of one, and the river's bend would once have made this northern end of the ridge a naturally defensible position worth occupying.

What survives today is a raised oval platform, roughly 37 metres across its longer axis and just over 30 metres across the shorter, defined by a scarp between one and two metres high. A fosse, the term for the encircling ditch that typically accompanied such an earthwork, is still faintly traceable along the south-south-west to west-north-west arc, though it has been reduced to a shallow depression no more than 20 centimetres deep and less than three metres wide at its base. Ringforts of this type are among the most common archaeological monument forms in Ireland, generally associated with early medieval settlement, typically between the sixth and tenth centuries, and often serving as enclosed farmsteads for a single family or small community. The hedge that now follows the scarp at Eden Island, along with a modern ramp entrance cut into the south-east side, speaks to the site's continued use as ordinary agricultural land long after its original function was forgotten. An original entrance gap remains visible at the south.