The Silk Road was unquestionably humankind’s mightiest river of commerce, ideas, and culture. The main Road branched off near Dunhuang, splitting north, where it skirted the Turfan Depression and the ultra-ﬁerce Taklamakan Desert via the oases at the foot of the Tien Shan, the Mountains of Heaven. The southern route was in its turn watered by the oases of the Kun Lun, perhaps the least known of the world’s great ranges. The two branches reunited at Kashgar but then threaded west into Persia and on to Europe, north into what is now Russia, and south into the Indian subcontinent, and each branch branched and braided, linking the boyars of old Rus with the mandarins of the Middle Kingdom and the sages of India with the emperors of Rome. Slowly, mysteriously, epically.