On the 1843 edition of the six-inch map, a roughly oval enclosure is clearly marked on a gradual west-facing slope near Garryroan, its outline measuring approximately 42 metres from north to south and tapering from around 24 metres wide at its southern end to just 14 metres at the north. By the time the revised edition appeared in 1906, it was gone from the map entirely, and today the field shows no visible trace of it above ground.

Enclosures of this kind are among the most common, and most frequently erased, monument types in the Irish countryside. They could serve a range of purposes depending on their period, from ringfort-style farmstead enclosures of the early medieval period to stock enclosures of various later dates. Without excavation it is rarely possible to say which a levelled example represents. What the Garryroan site does preserve, faintly, is the memory of its own existence: the field still shows what the notes describe as a lot of subtle undulations, the ground rising and dipping in ways that have no obvious agricultural explanation. These are the kinds of traces that reward a careful eye, the compressed archaeology of a structure that the plough has otherwise thoroughly erased between one map edition and the next.