St Januarius is the patron of Naples, and his devotion is an important part of the local culture.
In the city cathedral is kept a sample of the saint’s blood, which three times a year is ritually exposed to the public, each times reverting back to its liquid state. For the Catholic Church, this is classified as a miracle, while science is forced to suspend its judgement since no one is allowed to open the blood vial. Sometimes the ritual fails, and this is considered a bad omen.
Little is known about Januarius, but that he was a Bishop of Naples probably executed under Roman Emperor Diocletianus, who reigned from 284 to 305.