The first Sunday of October is one of the two days of the year for the plenary indulgence by reciting the Supplication to the Madonna of Pompeii. The other day for this is 8 May.
For more about the indulgence and prayers go HERE.
This devotion was started by Bl. Bartolo Longo, who had once been a Satanist “priest”. He converted, did penance, and became a lay Dominican. In 1872, Longo, a lawyer, went to Pompeii see to the affairs of Countess Marianna Farnararo De Fusco. He started there a Confraternity of the Rosary. They obtained a picture of the Blessed Virgin from a monastery, which before that was in a second hand store, before which they could recite the Rosary every day. It showed Mary with Sts. Dominic and Catherine of Siena. In 1875 Longo received permission to build a church. Miracles were reported and pilgrimages began. The picture has been restored several times since then. Longo also saw to the building of complex for works of mercy with orphans and prisoners. Pope John Paul II beatified Bartolo Longo in 1980. Some of his writings form the basis of the Luminous Mysteries of the Rosary.
You reach the sanctuary easily by walking just a few minutes out the back gate of the ancient ruins of Pompeii, famously destroyed by the eruption of Vesuvius in AD 79.