Bromo Tengger Semeru National Park, known locally as Taman Nasional Bromo Tengger Semeru (TNBTS) is a national park located in East Java, Indonesia, to the east of Malang and 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 (), 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 . The massif also contains the highest mountain in Java, Mount Semeru (), four lakes and 50 rivers. It is named after the Tengger Kingdom.