Billions of years old, the Usambara Mountains of eastern Tanzania are the sentinels of the Great Rift Valley plains. They clamber high above the Kenyan borderlands in a relief of bluffs and rock-ribbed escarpments, dressed neatly in a shroud of thick primeval jungle, clambering vines and cloud forests. But untouched the Usambara are not, for this is also one of the more densely inhabited regions of rural East Africa. Tin-roofed, thatch and timber villages stand testimony to the fascinating tribal presence, bearing the cultural hallmarks of the Maasai, the Shambaa and the Bantu to name just a few of the indigenous folk here. What’s more, trekkers now come by the bus load, all eager to case out the hiking trails that connect each rustic town stead, or discover hidden caves and waterfalls in the company of an experienced Usambara Mountains tour guide.