At Mullaghnashee in County Roscommon, what was once a cashel, a stone-built ringfort of the early medieval period, is now only legible from the air. Where a traveller on the ground would see level improved pasture, aerial imagery reveals the faint circular signature of a site roughly 52 metres across, its outline traced by the cropmark of a fosse, a surrounding ditch, somewhere between two and four metres wide. A gap of about six metres on the south-east side is likely the ghost of an original entrance, the point where people and livestock would have passed in and out of the enclosure perhaps a thousand or more years ago.

Older Ordnance Survey maps, both the 25-inch and the Cassini edition of the 6-inch, recorded the spot not as a monument but as an area of outcropping rock, which suggests the stone fabric of the cashel was already largely gone or unrecognised by the time systematic surveying began. A subrectangular depression running roughly west-northwest from the western edge of the enclosure, about 40 metres long and up to 12 metres wide, points to quarrying activity at some point, which would explain where much of the stone went. The site sits in what is now ordinary agricultural ground, with nothing visible at the surface to suggest its origins. About 300 metres to the south-east lies the holy well known as Toberbreedia, accompanied by a penitential station, a type of devotional site where prescribed circuits of prayer were performed. The proximity of an early enclosure to such a well is not unusual in the Irish landscape; secular and religious activity in the early medieval period often clustered in ways that left layered traces across quite small areas of ground.