In a pasture on a north-north-east-facing slope in Ballyduff, County Cork, a ringfort once stood near the edge of a steep drop down to a stream, and the only reliable witness to its shape is a map drawn in 1842. Today there is no visible surface trace; the site has been levelled, and the ground gives nothing away.

A rath, as this type of enclosure is also known, was typically a roughly circular earthwork enclosing a homestead, built and used through the early medieval period in Ireland. Thousands survive in various states across the country, but many more have been erased by centuries of farming and land improvement. This one in Ballyduff measured approximately 25 metres by 20 metres, making it a modest example of the type. What is unusual here is how clearly its former existence can be traced through a single cartographic source: the Ordnance Survey six-inch map of 1842 shows it as a hachured subcircular enclosure, the standard surveying convention for indicating an earthwork. More telling still, the line of the townland boundary was drawn to incorporate the fort's southern and western edges, suggesting the earthwork was already being used as a convenient landmark for administrative division, a common fate for such features even as they were beginning to disappear from the landscape.

There is nothing to see at ground level now, and the site sits on private agricultural land. Its interest lies less in what survives than in what the old map preserves: the ghost of an enclosure that once organised a small patch of north Cork, remembered only in the slight dogleg of a boundary line.