3. Sakurajima, Japan
Sakurajima used to be an island, until a volcanic eruption in 1914 connected it to the mainland by basically creating a bridge made of lava. The volcano is still active and spews out a steady plume. The ash particles often produce black rain. The 600,000 residents of nearby Kagoshima are under frequent evacuation alert due to seismic activity here, yet it is still a popular tourist attraction.