A souterrain, to use the proper term, is an artificial underground structure, typically built during the early medieval period in Ireland, constructed from dry-stone walling and roofed with large flat slabs. They appear across the Irish landscape in considerable numbers, associated most often with ringforts and early settlement sites, and their precise function has long been debated. Theories range from cold storage for dairy produce to places of refuge in times of raid or conflict, and in many cases they were probably used for both.

The Ballinlass example sits within a part of Galway that carries its own complicated history. Ballinlass is perhaps best known as the site of one of the more documented clearances of the nineteenth century, when in 1820 the Gerrard family evicted the entire population of the townland, tumbling some sixty or more houses to make way for grazing land. That human rupture is the more recent layer. Beneath it, the souterrain speaks to a much older pattern of settlement, one in which communities shaped the ground itself to serve their needs, hollowing out passages that have outlasted almost everything built above them. The fact that such a structure survives at Ballinlass is, in its quiet way, a reminder that the land held people long before the clearances and will hold the evidence of them long after.