The most important riverfor its flow and length in the department of Cusco (where, Machu Picchu is located) is called Huillcamayu (or willka-mayu) and Urubamba too.
This river is originated in la Raya (boundary of the departments of Cusco and Puno) more than 4000 meters above sea level. One of the most important tributaries of the Vilcanota river, for its flow and length, is the Sallqa river, that comes from the right side of the principal valley, at the Combapata town, around 100 km. Southeast of the city of Cusco.
The name "Sacred Valley of the Incas" comes from the translation of the quechua name of the river Willka-Mayu into the spanish, Willka means "Sacred", and mayu is "river" sacred River. This is an ancient name, here at the mountains the concepts river and Valley are inseparable.
Regarding the other name of the same river, the word Vilcanota, has its origin in the Aymara or colla language. (Colla or colla suyo was one of the four regions that formed the Incan Empire at the southeast of the imperial capital of the city of Cusco). A front-runner in history and archeology, Ernest W. Middendorff, wrote his famous book PERU after direct studies, visiting Peru between 1887 and 1888. He wrote about the matter as follows.
"The slopes at both sides of el paso (La raya) are high and steep. The western one opens forming a short and violent cliff, which ands in a high and glittering peak, this is the Vilcanota, one of the highest hills of the andean mountain range in ancient times this was a sacred place. It is told that it existed a famous temple of the sun that gave its name to the snowy peak, since Huillcanota is an aimara word that means "Casa del Sol" (Huillca significa in ancient aimara "The Sun", and then the genitive huillcana, syncope huillcan.Uta means "The House") eventhough the people in this town speak quechua, originally the mother tongue was aimara.
The term Vilcanota not only named the snowy peak, but the main river that started in its northwestern base. When this river comes into the territory of the province of Urubamba, it takes the name of this province, it is called Urubamba river.
The Sacred Valley of the incas comprises the area from the city of Sicuani (Province of Canchis, in the department of Cusco) up to the 122 km of the railroad that leads to Machu Picchu, at the House of Machines of the Hydroelectric. Sicuani is already a Valley because it is in a space limited by two pieces of mountain range, with a height estimated in 3450 meters above sea level, and the other and we said at the 122 km of the railroad) is al 1990 meters above sea level. The Valley is around 300 km. long.
The northern side of the Machu Picchu Archeological park is in the Sacred Valley of the Incas.