At Formoyle in County Sligo, a small enclosure once sat on the flat summit of a north-south ridge, now swallowed by coniferous forestry. Today there is nothing to see at ground level, no earthwork, no depression, no stony outline. The site has been entirely levelled, leaving behind only its cartographic ghost.

What we know of the enclosure comes from two nineteenth and early twentieth century editions of the Ordnance Survey six-inch map. On the 1837 edition it appears as a small, irregularly shaped feature, the kind of mark that surveyors noted when something on the ground caught their attention, even if its precise nature was unclear. By the 1912 edition it had been rendered as a hachured roughly circular enclosure, hachures being the short radiating lines used on older maps to suggest the raised or banked edges of a feature, with a diameter of approximately ten metres. That is a modest footprint, roughly the size of a large room, which might suggest a ring barrow, a small cashel, or any number of enclosed features common to the Irish landscape. Without surviving physical evidence, the specific function remains unknown. The site is classified as a potential monument, a designation that reflects genuine uncertainty rather than confirmed archaeological status.