Pompeii an ancient Roman city on the Bay of Naples 15 miles (24 km) southeast of Naples near the southern foot of Mount Vesuvius. In the eruption of Vesuvius in 79 A.D. Pompeii was buried in volcanic rock and ash. Its existence was completely forgotten within a few generations. The site was discovered in the 18th century and excavations were begun. Because it had lain undisturbed and protected from the elements since the time of the disaster, Pompeii gave the world its most precise knowledge of how a Roman city looked and how its inhabitants lived.