At Keamsellagh in County Galway, a souterrain, an underground stone-lined passage or chamber typically built during the early medieval period for storage or refuge, lies somewhere beneath the ground, blocked up and invisible, leaving no surface trace whatsoever. The site sits within a rath, a circular earthwork enclosure that once formed the farmstead of an early medieval family, and the combination of the two features would ordinarily make it a reasonably significant local monument. The word "ordinarily" is doing a lot of work here, because what distinguishes Keamsellagh is precisely the absence of anything to show for it.

The souterrain was recorded by McCaffrey in 1952, who noted it as blocked-up at that time, cataloguing it as entry number 73 in what appears to have been a systematic survey of the area. Even then, decades before the site received any formal archaeological designation, the passage was already sealed. Whether it was blocked deliberately in antiquity, collapsed naturally, or was simply infilled at some point in the intervening centuries between its construction and McCaffrey's visit is not recorded. What is certain is that nothing visible remains today on the surface to indicate it was ever there.