At Oghil in County Sligo, there is a ringfort that exists today only as a cartographic memory, its circular earthwork gone so completely that the pasture running along a north-south ridge gives no hint it was ever there.

A ringfort, or rath, is one of the most common early medieval monument types in Ireland, typically a circular enclosure defined by one or more earthen banks and ditches, used as a farmstead and place of refuge. The example at Oghil was recorded on the 1837 edition of the Ordnance Survey six-inch map as a circular enclosure of around twenty metres in diameter. That map, produced during the first comprehensive survey of Ireland, captured the site at a moment when it was presumably still legible on the ground. At some point after that survey, the enclosure was levelled entirely, almost certainly through agricultural improvement or land clearance, and no remains are now visible at ground level.