Hachures, the short radiating lines cartographers used to suggest slopes and depressions, hinted at something worth noting on the ground, though the map offered no label. When someone finally went to look in 1983, the feature turned out to be a quarry, most likely worked at some point after 1700. That gap between the mark on the paper and the physical reality it described sat unresolved for several decades, which is a quietly odd fate for something as straightforward as a hole in the ground.