A slight rise in the ground is about the sum of it, and even that is easy to miss. Yet beneath the grass lies the ghost of an earthwork enclosure, levelled so thoroughly that its existence would be little more than a rumour were it not for a handful of maps and a satellite camera passing overhead.

The site first came to attention during the Castleisland District Archaeological Survey in 1985, which noted the gentle swell in the ground as a probable indicator of a levelled earthwork. Earthwork enclosures of this kind, which typically took the form of a raised bank and ditch defining a roughly circular area, were built throughout Ireland across many centuries and served a wide range of purposes, from farmstead boundaries to ritual or ceremonial use. What makes the Glanshearoon example particularly curious is its cartographic story. The enclosure appears on the Cassini edition of the Ordnance Survey six-inch map, suggesting it was still legible as a feature when that revision was recorded, yet it is entirely absent from the 1841 edition of the same map series. That absence from the earlier survey may simply reflect the limits of what surveyors recorded at the time, or it may hint at something about when the earthwork was finally reduced to near nothing. The picture sharpened further when a Digital Globe orthoimage captured between 2011 and 2013 revealed a cropmark, the faint but telling variation in vegetation growth that can betray a buried or heavily disturbed structure long after the surface has been smoothed over by ploughing or grazing.