From Wikipedia: http://en.wikipedia.org/wiki/Usambara_Mountains
The Usambara Mountains are a mountain range in North-East Tanzania, approximately 90 km long and ranging from 30 to 50 km in width. They are part of the Eastern Arc Mountains, which stretch from Kenya through Tanzania, and are one of the world’s Biodiversity hotspots. The range is accessible from the towns of Lushoto in the West, and Amani in the East. The Usambaras are commonly split into two sub-ranges, the West Usambara and the East Usambara. The East Usambara is closer to the coast, receives more rainfall, and is significantly smaller than the West Usambara.