on june 18, 1656 a part of the plaster peeled off a wall inside the church of st. mary in vivario, and an ancient fresco became visible. it was the image of saints sebastian and roch, protector from the plague. in that same year there was an epidemic of plague in rome but frascati was unaffected. since that year, the two saints have been co-patron saints of the city. there are statues of the two saints in the façade of the cathedral.