Bromo Tengger Semeru National Park is the largest volcanic region in the province of East Java, Indonesia, covering a massive area of 800 square km. For anyone with even a passing interest in volcanoes, a visit to the park is a must. Within the 10 km, barren, desert-like caldera, called the sea of sand, sit the volcanic cones of Mt. Batok and Mt. Bromo. The latter is still active, with a cavernous crater from which smoke blows skyward.