The valley was formed by the Urubamba river, also known as the Vilcanota River, Willkanuta River (Aymara, "house of the sun") or Willkamayu (Quechua). The latter, in Quechua, the still spoken "lingua franca" of the Inca Empire, means the "sacred river". It is fed by numerous tributaries which descend through adjoining valleys and gorges, and contains numerous archaeological remains and villages. The Sacred Valley was the most important area for maize production in the heartland of the Inca Empire and access through the valley to tropical areas facilitated the import of products such as coca leaf and chile peppers to Cuzco.