A deafening boom roars through Pompeii´s crowded marketplace. The ground shakes violently, throwing midday shoppers off balance and toppling stands of fish and meat. People scream and point toward Mount Vesuvius, a massive volcano that rises above them.Nearly 2,000 years ago, Pompeii was a bustling city located in what is now southern Italy. But in the summer of A.D. 79, the nearby Mount Vesuvius volcano erupted. It spewed smoke and toxic gas 20 miles into the air, which soon spread to the town. Almost overnight, Pompeii—and many of its 10,000 residents—vanished under a blanket of ash.