Kawah Ijen Volcano is the largest acidic crater lake in the world know to have two of the most unusual occurrences on Earth.The first is an active solfatara that emits hot, flammable sulfurous gases. Some of the gas condenses in the atmosphere to produce flows of molten sulfur that also burn with an electric-blue flame. The flames are difficult to see during the day but illuminate the landscape at night.The second occurrence is a one-kilometre-wide caldera lake filled with turquoise-blue water. The colour of the water is a result of its extreme acidity and a high concentration of dissolved metals.
Ijen Crater is the biggest crater lake in Java. The sulfur crater lake lies between a natural dams of deeply etched rock. It is 200 meters deep and contains about 36million cubic meters of steaming acid water, shrouded in a smelling swirling sulfur cloud. Inside the crater the different color and size of stones are found. Indeed the crater of Ijen is beautiful garden of stone as well. The principal attraction at Ijen is the large Crater Lake that has much sulfur, which lies hidden between sheer walls of deeply furrowed rock at more than 200 meters. The Ijen crater itself lies at approximately 2,300 meters above sea level. It forms a twin volcano with the now extinct Mount Merapi. The enormous Crater Lake, which is 200 meters deep and covers an area of more than meters, a million square meters, contains about 36 million cubic meters of steaming, acid water. Reach Ijen by late evening & this night you will be awake all night to witness a visual spectacle like never before in your life. Be prepared to stay awake all night, As such you will not even know when the night started & when the day break happened. Get down from the crater early in the morning, reach Banyuwangi after breakfast. Sleep for the rest of the day & visit local places in the evening.