a river in central Peru. The Urubamba is 725 km long. The river, which is known as the Vilcanota in its lower course, rises on a massif that forms a watershed in the Central Andes. The river flows through deep canyons that dissect the Cordillera de Vilcanota and the Cordillera Vilcabamba. The Urubamba merges with the Apurímac (Tambo) to form the Ucayali River of the Amazon River basin. Freshets occur between December and February. A hydroelectric power plant is on the river. On a mountain above the Urubamba are the ruins of the city of Machu Picchu.