The rath at Lahaghglass in County Galway belongs to that category. Standing in the reclaimed pastureland where it once lay, there is nothing to see, no earthwork, no raised ground, no depression, no scatter of stone. The site survives only as a notation on the first edition of the Ordnance Survey six-inch map, where a roughly circular enclosure of around 45 metres in diameter is recorded, its south-western to west-north-western arc once bounded by a road.

A rath, sometimes called a ringfort, is an enclosed farmstead of the early medieval period, typically dating from roughly the fifth to the twelfth century. These earthen or stone-banked enclosures were once among the most common field monuments in Ireland, numbering in the tens of thousands, and they served as the domestic unit of rural life for much of the first millennium. The example at Lahaghglass would have been a modest one by the measure of its diameter, the kind of enclosure associated with a single farming family rather than a person of significant rank. What finished it off here was the process of land reclamation, the levelling and drainage of pastureland that accelerated across Connacht during the eighteenth and nineteenth centuries, and which quietly erased features that had endured for over a thousand years. By the time surveyors arrived to compile the first Ordnance Survey maps in the nineteenth century, the enclosure was already reduced enough that the road formed part of its visible boundary, rather than running around it as an obstacle.