B. Yeats purchased in 1917 and made famous through his poetry. Less celebrated, and easy to overlook entirely, is the presence of a souterrain somewhere in the same landscape, a reminder that the ground beneath Yeats's romantic retreat has a much older story to tell. Souterrains are stone-lined underground passages or chambers, built during the early medieval period, roughly the sixth to the twelfth centuries, most likely for cold storage, refuge, or both. They are found across Ireland in their hundreds, often associated with ringforts, and their entrances are frequently small enough to require crawling, which may well have been part of their defensive logic.

Beyond its location in the Ballylee townland, the specific details of this particular souterrain, its dimensions, condition, associated surface features, and precise relationship to the wider archaeological landscape of the area, remain a matter for further research. What can be said is that its existence in this part of east Galway is not surprising. The region was well settled in the early medieval period, and souterrains tend to cluster in areas of sustained agricultural activity, tucked beneath the remains of enclosed farmsteads whose earthworks have often been levelled by centuries of ploughing. The proximity to Thoor Ballylee, itself a medieval structure later adapted and layered with literary meaning, gives the site an additional texture, two different eras of human occupation sharing the same small patch of ground.