Ital. Vesuvio, only active volcano on the European mainland, S Italy, on the eastern shore of the Bay of Naples, SE of Naples. The height of the main cone changes with each eruption, varying within a few hundred feet of the 4,000-ft (1,219-m) level; in 1969 the height was 4,190 ft (1,277 m). The second summit, Monte Somma (3,770 ft/1,149 m) is a ridge that half encircles the cone and is separated from it by a valley (c.3 mi/5 km long). The sides of Vesuvius are deeply scarred by lava flow, but its lower slopes are extremely fertile, dotted with villages, and covered with vineyards which produce the famous Lachryma Christi wine. The base of the mountain (circumference c.45 mi/70 km) is encircled by a railroad, and a chairlift reaches almost to the rim of the crater (diameter c.2,300 ft/700 m). On the western slope, at 1,995 ft (608 m), there is a seismological observatory (built 1840–45). The outline of Vesuvius forms part of the backdrop of Naples; it is often surmounted by a faint plume of smoke.