Man-made underground passage in Shanakill Upper

Shanakill Upper holds a seven-and-a-half-metre semicircular trench in the northeast quadrant of its ringfort, shallow enough to wade but deep enough to swallow a knee. Flat sandstone blocks line the bottom like forgotten capstones, waiting for a roof that never came or a door that broke long before memory. The trench may have been a cellar, a drainage cut, or a failed attempt to build beneath the fort rather than beside it. In any case, someone measured the curve, dug through solid ground, and left the shape sharp enough that the hill still remembers the effort.