The Mekong river bends southwest; over a reach of more than 125 miles (200 km) it forms the Myanmarese-Laotian border. Although two great roads cross it—the caravan route from the southeast to Lhasa and the road from Kunming to Myanmar—much of the river valley in the highlands of Tibet and Yunnan is remote and sparsely populated. Below Myanmar, the river basin may be divided into six major sections on the basis of landforms, vegetation, and soils: the northern highlands, Khorat Plateau, eastern highlands, southern lowlands, southern highlands, and delta. Most of the vegetation in the lower basin is of the tropical broad-leaved variety, although the occurrence of individual species varies with latitude and topography.