Where is this volcano that spews "blue fire"?

Kawah Ijen is Indonesia’s most formidable volcano with a fascinating moniker - “The Blue-Fire Volcano”.

Located on the island of Java, in Indonesia, the volcano boasts two of the most unusual geological occurrences on Earth. Instead of producing the usual red lava and black smoke, the volcano’s underground activities cause it to emit electric-blue flames from its solfatara (the name for a volcanic crater emitting only sulfurous and other gases). The flammable sulfur gases ignite as they enter Earth's oxygen-rich atmosphere, and burn with an electric blue flame. Some of the gas condenses in the atmosphere, producing bright blue flows of molten sulfur. Unlike regular volcanoes whose bright red lava is visible even in daylight, Kawah Ijen’s blue burning flames can often only be seen at night.

The second oddity is a one-kilometer-wide caldera lake filled with turquoise-blue water. The color of the water is a result of its extreme acidity and a high concentration of dissolved metals. It is the world's largest highly acidic lake with a measured pH as low as 0.5. The cause of its acidity is an inflow of hydrothermal waters charged with gases from the hot magma chamber below. While the turquoise water of this crater lake is quite spectacular, it is also life-threatening.

Visitors hoping to see this unique spectacle at its best, have to hike about 10,000 feet at night; making the trek with a guide is highly advised.