The Roman city of Pompeii in A.D. 79 was a thriving provincial centre, a few miles from the Bay of Naples, with a population of between 10,000 and 20,000 people. Its narrow streets, made narrower by street vendors and shops with cloth awnings for shade, were full of shoppers, tavern-goers, slaves, and vacationers from the North. A huge new aqueduct supplied running water from the Lower Apennine mountains, which flowed from fountains throughout the city, even in private homes. But the key to Pompeii’s prosperity, and that of smaller settlements nearby like Oplontis and Terzigna, was the region’s rich black earth provided by Mount Vesuvius’ volcanic eruptions. “One of the ironies of volcanoes is that they tend to produce very fertile soils, and that tends to tempt people to live around them”, says geologist Philip Janey. Had Roman knowledge in the summer of A.D. 79 been less mythological and more geological, the Pompeiians might have recognized the danger signs from Mount Vesuvius and escaped the volcanic eruption that was to follow.