The traverse from Lhasa to Zham at the Chinese border with Nepal, along the Tsangpo valley and through the Himalaya, is one of the most marvelous of geological field trips. The journey takes a minimum of 3 days by car on adequate, mostly dirt, roads. Roadside outcrops reveal much of what happened between the opening of a part of the Neotethyan ocean about 250 m.y. ago, and the collision of India with Asia 200 m.y. later. The building of the world's highest mountain chain as a result of the collision has exposed rocks from the seafloor and beneath in thousands of superb outcrops, and in the clear, thin air of the high altitudes, impressive geological structures are laid out on remote mountainsides.