The Chittagong Hill Tracts (CHT) occupies a physical area of 5.093 sq. miles (13,295 sq.km), constituting ten per cent of the total land area of Bangladesh. The region comprises three districts: Rangamati, Khagrachari, and Banderban. The districts comprise seven main valleys formed by the Feni, Karnafuli, Chengi, Myani, Kassalong, Sangu and Matamuhuri rivers aid their tributaries and numerous hills, ravines and cliffs covered with dense vegetation, which are in complete contrast to most other districts of Bangladesh, which consist mainly of alluvial lands. Geographically the CHT can be divided into two broad ecological zones: (a) hill valley, (b) agricultural plains. It is surrounded by the Indian states of Tripura on the north and Mizoram on the east, Myanmar on the south and east and Chittagong district on the west.