Pompeii is a volcano.
Pompeii was an ancient Roman town-city near modern Naples , in the Campania region of Italy , in the territory of the comune of Pompei . Pompeii , along with Herculaneum and many villas in the suzrrounding area , was mostly destroyed and buried under 4 to of volcanic ash and pumice in the eruption of Mount Vesuvius in 79 AD . It came under the domination of Rome in the 4th century BC , and was conquered and became a Roman colony in 80 BC after it joined an unsuccessful rebellion against the Roman Republic . By the time of its destruction , 160 years later , its population was estimated at 11,000 people , and the city had a complex water system , an amphitheatre , gymnasium , and a port .