An enclosure roughly eighteen metres across once occupied a gentle south-westerly slope just above the water, positioned at the crossing point to Scanlon's Island. Today, no physical trace of it remains in the ground.

The enclosure first entered the documentary record through the 1842 Ordnance Survey six-inch map, where it appears as a circular feature marked with hachures, the small lines surveyors used to indicate an earthwork or raised boundary. By the time it was formally listed in the Record of Monuments and Places in 1996, the feature had already been categorised simply as an enclosure, a catch-all term for a bounded space of uncertain age and function. Whether it was a rath, the earthen ringfort type common across early medieval Ireland, or something older or more utilitarian, is now impossible to say. What the landscape around it does suggest is a cluster of related activity: a rath sits roughly two hundred metres to the north-west, and a cashel, a stone-walled enclosure of broadly similar period and purpose, lies around five hundred metres to the south-south-west on Scanlon's Island itself. A cashel uses dry-stone construction where a rath uses earth and bank, but both served broadly comparable roles in early medieval settlement. The lost enclosure at the crossing point may have functioned as part of this same loose network, perhaps marking or controlling the route between the mainland and the island.