San Gennaro (St Januarius) has a chapel in Naples Cathedral to himself, a church within a church, a bombastic Counter-Reformation affair of precious metals and rich marbles, encrusted with busts and frescoed to the rafters. The decoration celebrates his status as protector of Naples against pestilence, disaster and Vesuvius. The volcanic eruption on 16 December 1631 was the most severe since the one that entombed Pompeii. Since at least the 17th century, Neapolitans have been giving the saint three chances a year to prove himself, through the miraculous liquefaction of his blood, encased in two phials within an ornamental glass reliquary.