river in the Amazon drainage system, rising in the Andes of southern Peru. It flows for about 450 miles (725 km) to its junction with the Apurímac, where it forms the Ucayali. The upper part of the Urubamba, there called the Vilcanota, flows past the towns of Sicuani, Urcos, and Urubamba and is densely settled by Indian farmers. Below Urubamba, in the Gorge of Torontoy, the river plunges from 11,000 to 8,000 feet (3,400 to 2,400 m) in 20 miles (32 km). The railroad from Cuzco to Aguas Calientes, popular with tourists headed to Machu Picchu, parallels this portion of the river. The lower course, downstream from Quillabamba, is sparsely populated.