The Ijen volcano complex is a group of composite volcanoes in East Java, Indonesia, near the Banyuwangi and Bondowoso regencies. It is notable for its blue fire, acidic crater lake, and laborious sulfur mining. The Ijen volcano, located west of Gunung Merapi, has a turquoise-colored acidic crater lake one kilometer (0.62 miles) wide.
The lake is the site of a labor-intensive sulfur mining operation, in which sulfur-laden baskets are carried from the crater floor by hand. The work is well compensated in comparison to the cost of living in the area, but it is physically demanding. Workers earn about US$13 per day and must transport sulfur chunks three kilometers to the nearby Paluding Valley to be compensated.