Volcanoes make some of the most dramatic skylines on earth. Any city lying in their shadow practically feels mythic.
Take Pompeii, which was a favorite place for Roman Empire elites to vacation before Mount Vesuvius blew its top in A.D. 79, raining down a 13-mile-high rocky plume of debris while a pyroclastic flow -- a superheated combination of molten rocks, ash, and poisonous gas -- rocketed toward the city at hundreds of miles per hour. In a flash, 2,000 lives ended.
Pompeii's legacy is so iconic, it's hard to imagine a volcano dealing a similar blow in modern times, but it has happened -- and could possibly happen again.
Since 1900, at least three major urban zones have been hit by eruptions: St. Pierre, the capital of Martinique (1902); the Colombian city of Armero (1985); and Plymouth, the capital city of Montserrat (1995). When Mount Tambora in Indonesia erupted in 1815, its plume blocked so much sun that New York City saw snow on June 6 the following year.
But just because there's a volcano on the horizon doesn't mean you necessarily need to worry.
"Most volcanic eruptions are not large, and cities are not seriously impacted," says Henry Gaudru, president of the European Volcanological Society (SVE) and advisor to the UN's Decade Volcanoes project, which monitors the 16 most potentially destructive volcanoes on earth. Even though 500 million people worldwide may be directly exposed to volcanic risk, the United States Geological Survey's Global Volcanism Program counters that prediction methods (like tracking magma temps in "dormant" volcanoes) have never been better.
Still, with the help of these experts, we've compiled a list of 15 cities that are most at risk of being affected by volcanic eruption. They may not be in immediate danger, but consider a visit sooner rather than later...just in case.