Bromo Tengger Semeru National Park

This national park is named after its two mountains, Mount Semeru (the highest in Java at 3,676m), Mount Bromo (the most popular) and the Tengger people who inhabit the area. Mount Semeru also known as Mahameru ("Great Mountain"), is one of Indonesia's most active volcanoes. What stands out most about this mountain is the fact that it erupts periodically (and very reliably). Every 20min or so, the volcano belches out a huge cloud of steam and smoke, sometimes interspersed with ash and stones. Climbing Mount Semeru requires some planning and a permit from the national park authority. The mountain is often closed due to its highly active nature. Mount Bromo (2,329m) is easily recognized as the entire top has been blown off and the crater inside constantly belches white sulfurous smoke. It sits inside the massive Tengger caldera. with a diameter of approximately 10km, surrounded by the Laut Pasir (Sea of Sand) of fine volcanic sand. The overall effect is unsettlingly unearthly, especially when compared to the lush green valleys all around the caldera.