The only place on Earth where you can witness luminous blue fire inside a volcano is Kawah Ijen, located in Indonesia. The eerie blue glow is not lava—it’s caused by ignited sulfuric gases that emerge at extremely high temperatures and burn with an electric-blue flame when they contact oxygen. The phenomenon is visible only at night and has made Ijen one of the most unusual geological sites on the planet. Key Facts: • Only volcano with visible blue flames • Caused by burning sulfuric gases, not