The historian Diodorus Siculus said that there was a story that Hercules once passed through the country of Cumae when he was going to Sicily . There , he found a place called `` the Phlegraean Plain '' ( phlegraion pedion , `` plain of fire '' ) . The historian , Diodorus Siculus , relates a tradition that Hercules , in the performance of his labors , passed through the country of nearby Cumae on his way to Sicily and found there a place called `` the Phlegraean Plain '' ( phlegraion pedion , `` plain of fire '' ) , `` from a hill which anciently vomited out fire ... now called Vesuvius . ''