Three times a year, towns around the Bay of Naples wait for news from two sealed vials.
They are said to hold the blood of the city's patron saint, and the faithful watch for it to turn from solid to liquid. Spectrographic studies suggest hemoglobin may be inside, though the vials have never been opened. Neapolitans take a failure seriously: the blood stayed solid in 1944, when Vesuvius last erupted, and in 1967, the year of an earthquake.