Ijen plateau or known as "Kawah Ijen" is highly recommended to mountain buffs and hikers. The Plateau was at one time a huge active crater, 134 sq km in area. Today, Ijen is a quiet but active volcano, and the landscape is dominated by the volcanic cones of Ijen (2,368 asl) and Merapi (2,800 asl) on the northeastern edge of the Plateau, and Raung (3,332 asl) on the southwest corner.
The magnificent turquoise sulfur lake of Kawah Ijen lies at 2148 m above sea level and is surrounded by the volcanos sheer crater walls. The vent is a source of sulfur and collectors work here, making the trek up to the crater and down to the lake every day. Sulfur collectors hike up in the morning and return around 1 pm when the clouds roll in. They carry shoulder basket of pure sulfur from a quarry on the lakes edge under the shadow of the sheer walls of the crater. The mineral at Kawah Ijen is purer and is worth commercial exploitation despite the horrendous labor involved: Javas homegrown sulfur is a natural source of sulfuric acid, in great demand in the oil-refining business and in the production of fertilizers.