It's not fast, but it's high. Tops out at 17,000ft on the way from Chinese Turkestan over the "Roof of the World" to Pakistan. This place here is called the Gez Defile. It's a gnarly gash that drops down from the Pamir Plateau into the Takla Makan desert, which means "you go in but you don't come out." The peak is Kongur, somewhere north of 25,000ft up.