Source: Map showing the Urubamba River from Cuzco to Manaus, Brazil.
Comments: At the bottom left, find Cusco. Then, just NW of Cusco, find the archeological site of Machu Picchu (a triangle of 3 dots). Follow the thin blue line N from there to the region of Ucayali. The blue line (the river) is wider there. Then follow that line (the river) to the upper left of this map segment at Iquitos (there's an airport symbol there). Then follow the river from the upper left to the upper right along the Solimões River to Manaus. Below Manaus the river changes names to the Amazonas.