The site at Nantinan sits within a rath, a type of circular earthwork enclosure built during the early medieval period, typically used as a farmstead and defended by one or more earthen banks. This particular rath is now used as a garden, which is unremarkable enough on its own. What makes the place quietly odd is what local accounts suggest lies beneath it, or once lay beneath part of it, and what the ground itself still seems to be hinting at.

A souterrain is a man-made underground structure, usually stone-lined, associated with raths across Ireland. They were used for storage, shelter, or escape, and were often carefully concealed. At Nantinan, local information indicates that one was uncovered when the northern half of the rath was levelled some decades ago. Whether it was fully excavated, partially disturbed, or simply exposed and then forgotten is not recorded. What remains is a faint trace on the surface: an irregular area of differential plant growth occurring approximately within the original northern sector of the rath, the kind of variation in vegetation that can indicate disturbed or hollow ground beneath. It is indirect evidence, the landscape registering something that is no longer visible, but it is the sort of detail that archaeologists take seriously.