Mount Ijen (Kawah Ijen)

Mount Ijen (Kawah Ijen) is an active volcano on the border of Bondowoso and Banyuwangi Regencies in East Java, Indonesia. It is notable for its large turquoise acidic crater lake, the world's largest, and the rare electric-blue flames caused by ignited sulfuric gases. Part of the Ijen UNESCO Global Geopark, it is famous for traditional sulfur mining and sunrise trekking.

Visitors hike approximately 3 km from Paltuding Basecamp to the crater rim (2,443m elevation) then descend to the crater floor. Expect a steep, rocky trail, views of the turquoise acidic lake, active sulfur vents, traditional sulfur miners carrying loads, and the blue flames visible only in pre-dawn darkness. The summit offers sunrise views over the Ijen caldera and surrounding volcanoes.

Mount Ijen is part of the Ijen volcano complex, a group of stratovolcanoes within a 20 km wide caldera. The crater lake is highly acidic due to hydrothermal activity. Sulfur mining has been conducted since the Dutch colonial period and continues as a traditional industry, with miners extracting sulfur from vents on the crater floor.

The site is culturally significant for the traditional sulfur miners who manually carry sulfur loads of 70-90 kg from the crater. The area is within the Osing cultural region and is part of the Ijen UNESCO Global Geopark, recognized for its geological and cultural heritage.