No earthwork, no hollow, no tell-tale depression in the ground gives it away. The site belongs to a category of underground structure known as a souterrain, a type of dry-stone tunnel common in early medieval Ireland, typically associated with ringforts and thought to have served as places of refuge, food storage, or concealment. What makes this particular example quietly striking is its complete invisibility from above.

When McCarthy examined the site in 1977, he found a stone-built passage with corbelled side walls, meaning the stones were laid in overlapping courses leaning inward rather than mortared vertically, a technique that gives the structure its self-supporting strength. Even then, only a portion of the passage could be entered; the remainder had already collapsed. The souterrain sits within what is believed to be a ringfort, the circular enclosure of banked earth or stone that served as a farmstead for much of early medieval Ireland, though the ringfort itself has left no clear trace either. Both the enclosure and its underground annex have effectively vanished back into the landscape.