A broad oval earthwork sits in undulating grassland beside a stream in north County Galway, and most visitors would walk past it without a second glance. Yet the geometry is still there if you know where to look: a subcircular enclosure measuring roughly 41 metres across its north-east to south-west axis, defined in places by an earthen bank and, in others, by a quarried-out scarp where stone was removed at some point, leaving a raw edge in place of the original rampart.

This is a rath, the most common type of early medieval settlement monument in Ireland, typically consisting of a raised circular or oval area enclosed by one or more earthen banks and external ditches. Raths were generally farmsteads, home to a single family and their livestock, and they were built in their thousands across the Irish countryside between roughly the fifth and twelfth centuries. The Ballyglass example retains its bank along the north-west through to the east, while the accompanying fosse, a defensive ditch dug outside the bank, survives only as a slight depression curving from the north-north-east around through the east to the south-south-east. More intriguing is what may lie beneath the surface: a probable souterrain has been identified within the interior. A souterrain is an underground stone-lined passage or chamber, built during the early medieval period and thought to have served variously as a refuge, a cool store for food, or a means of escape. Whether this one was ever fully excavated or recorded in detail is not clear from what is currently known.

The site is low-key to the point of near-invisibility, which is itself a kind of interest. Earthworks like this one have survived not through formal protection but through the quiet indifference of the landscape around them, grazed over and gradually worn down, their original profile softened by centuries of weather and agricultural activity.