There are some major contrasts in the south of Bolivia, partly because it is so huge. Potosí, steeped in history, most of it bloody, is high, cold, and barren. Tarija, up against the Argentine border, is warm, friendly, and easygoing. Sucre is somewhere in the middle, an earnest university town and the capital of Bolivia. The Salar de Uyuni is, quite simply, out of this world.