The western section of the region, among Java's most rugged, isolated the eastern salient from Java's central heartland to its west. The Tengger massif (including Mount Bromo), and Mount Semeru, Java's highest peak, lie in this section. Together they form the Bromo Tengger Semeru National Park. The Iyang-Argapura massif lies in the central section, and the Ijen composite volcano lies in the eastern section.