Arunachal Pradesh can be broadly divided into 5 physiographic zones: the Eastern Himalayan Ranges, the Sub-Himalayan Ranges, the Brahmaputra Valley, the Patkai Hills, and the Mishmi Hills.
The Eastern Himalayan Ranges are the highest and most rugged physiographic zone in Arunachal Pradesh. They are composed of young, folded mountains that are still rising. The highest peak in Arunachal Pradesh, Mount Gorichen, is located in this zone.
The Sub-Himalayan Ranges are a series of lower, less rugged mountains that lie to the south of the Eastern Himalayan Ranges. They are composed of older, more stable rocks. The Sub-Himalayan Ranges are home to a number of important rivers, including the Brahmaputra and the Dibang.
The Brahmaputra Valley is a broad, fertile valley that lies between the Eastern Himalayan Ranges and the Sub-Himalayan Ranges. It is the most densely populated region in Arunachal Pradesh. The Brahmaputra River is the main river in the valley.
The Patkai Hills are a low, forested range of hills that lie to the south of the Brahmaputra Valley. They are a transitional zone between the Himalayas and the Indo-Gangetic Plain. The Patkai Hills are home to a number of important wildlife sanctuaries, including the Namdapha National Park.
The Mishmi Hills are a high, forested range of hills that lie to the east of the Brahmaputra Valley. They are the easternmost physiographic zone in Arunachal Pradesh. The Mishmi Hills are home to a number of indigenous tribes, including the Mishmi people.