The seat of Tibet’s ancient emperors, Tsetang, on the Tsangpo (Brahmaputra) River 113 miles (183km) southeast of Lhasa, is the region’s fourth city and most convenient base for exploring the spectacular valleys to its south, where a number of ancient monasteries reside amidst a landscape of surreal grandeur. Foremost among them is Yumbu Lakhang, whose distinctive whitewashed tower surveys a sublime spread of cloud-swept peaks from its rock perch above the Yarlung Valley. A Buddhist shrine has stood on this spot for 2,000 years, making it the oldest temple in Tibet.