kawah ijen volcano

Sulfur deposits at Kawah Ijen (green crater) Volcano in Eastern Java, Indonesia. Volcanic gases from the fumaroles in this crater not only deposit the sulfur but make the lake extremely acid -- both sulfuric and hydrochloric.
The IJen Plateau lies in the centre of the ijen - Merapi - Maelang Reserve, which extends over much of the mountainous region to the west of Banyuwangi, bordering or, the Baluran National Park. A luminous blue/green crater lake lies at the far eastern end of the plateau and is without doubt one of the most impressive of East Java's natural wonders.
The lake can be reached from either the east or the west. The latter is the more popular approach, since it takes just an hour and a half to hike up the mountainside from the road's end. From the Banyuwangi side, however, the trek takes six to seven hours from the village of Licin.
Kawah IJen is 2,300 metres above sea-level. The enormous lake, which is 200 metres deep, contains approximately 36,000,000 cubic metres of steaming, acid water. A walk around the crater takes a full day.