Mount Bromo In Indonesia is the important mountain.Mount Bromo (2,392m) is an active volcano in the Bromo-Tengger-Semeru National Park of East Java, Indonesia. Bromo is not the highest mountain in Java - that honor goes to nearby Mount Semeru at 3,676m - but it is probably the most famous one. Bromo is in fact only one of many peaks inside the massive Tengger Caldera, but it's easily recognized as the entire top has been blown off and the crater inside constantly belches white sulphurous smoke. The inside of the caldera, aptly dubbed the Laut Pasir (Sea of Sand) is coated with fine volcanic sand and the overall effect is unsettlingly unearthly, especially when compared to the lush green valleys all around the caldera.