There is nothing to see, no depression, no earthwork, no trace of stone; just ordinary ground concealing what was once a deliberate underground construction.

Souterrains are man-made underground passages or chambers, typically cut into earth or built from stone, and associated in Ireland with early medieval settlement, roughly the period between the seventh and twelfth centuries. They are found across the country in considerable numbers, most often connected to ringforts, and their purpose is still debated, though storage and refuge are the explanations most commonly advanced. The example at Crohane is of the earth-cut variety, meaning it was dug directly into the subsoil rather than lined or roofed with stone slabs. It was investigated in 1977 by researchers from University College Cork, and that investigation remains the only reason the site appears in the archaeological record at all. Without it, the souterrain would be entirely unknown. No surface feature survives to betray its presence.