The volcanic complex of Tengger forms a condition where a new caldera of volcano forms inside a larger and more ancient caldera. There are five volcanoes inside the Tengger Caldera: Mount Bromo (2,329 m), Mount Batok (2,470 m), Mount Kursi (2,581 m), Mount Watangan (2,661 m), and Mount Widodaren (2,650 m). Mount Batok is the only peak that is no longer active, and is covered in casuarina () trees. Mount Widodaren, located beside Mount Batok, contains the cave Widodaren, which is considered sacred by local people.