The rhinoceros area in Nepal covers approximately 1,250 square miles, comprising the valleys of the Rivers Narayani, Rapti, and Reu. Although it is dun country, it contains most of the sub-tropical vegetation usually associated with terai country, and can roughly be divided into (1) riverain, (2) grassland above flood level, and (3) sal forest. The hills are almost entirely under sal (Shorea robusta), a valuable hardwood.