Popocatépetl, Mexico
Not too far east of Mexico City, this snow capped volcano has erupted no less than 20 times since 1519. Nearly 9 million people live within its blast radius. It last erupted 17 years ago, but thanks to perfectly executed evacuation procedures, 41,000 people from surrounding towns got away safely.
*heck
More like 14 million!
1.6 million people in 1951.