The Usambara's are a part of the ancient Eastern Arc chain which mountains stretch in a broken crescent from the Taita hills in southern Kenya down to Morogoro and the southern highlands. They are estimated to be at least 100 million years old and the rocks forming them may be as much as 600 million years old. The mountains are home to an exceptional assortment of plants and animals and represent one of the highest degrees of biodiversity on the continent.
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.