Bromo Tengger Semeru National Park (Indonesian: Taman Nasional Bromo Tengger Semeru; abbreviated as TNBTS) is a national park located in East Java, Indonesia, to the east of Malang, to the west of Lumajang, to the south of Pasuruan and Probolinggo, and to the southeast of Surabaya, the capital of East Java. It is the only conservation area in Indonesia that has a sand sea, the Tengger Sand Sea (Indonesian: Laut Pasir Tengger), across which is the caldera of an ancient volcano (Tengger) from which four new volcanic cones have emerged. This unique feature covers a total area of 5,250 hectares at an altitude of about 2,100 meters (6,900 ft). The massif also contains the highest mountain in Java, Mount Semeru (3,676 meters (12,060 ft)), four lakes (including, the isolated Ranu Tompe), and 50 rivers. It is named after the Tenggerese people. The explosion of the volcano that created the caldera, happened ca. 45.000 years ago, in an event similar to the Krakatau eruption.
The Tengger Sand Sea has been protected since 1919. The Bromo Tengger Semeru National Park was declared a national park in 1982.
