The ground is ordinary grassland. No earthwork rises from it, no stones break the surface, no outline suggests that anything was ever here. Yet the site is real, and it was only when LiDAR imagery, a remote-sensing technology that uses laser pulses to detect subtle variations in ground elevation, was applied to the landscape that a small, circular enclosure emerged from the data, invisible to anyone walking the field above it.

The enclosure sits in a remarkably dense stretch of early medieval remains. A barrow, a burial mound of a type constructed across Ireland from the Bronze Age onwards, lies around 135 metres to the north-north-west. A ringfort, the circular enclosed farmstead that was the standard unit of rural settlement in early medieval Ireland, sits about 100 metres to the south-south-east. The levelled enclosure at Portnashangan belongs, almost certainly, to the same broad period and pattern of activity, though the precise function of such small circular features can be difficult to determine without excavation. What is clear is that the ground here was once organised, enclosed, and used in ways that left only the faintest of traces.