Across plains watched over by soaring eagles, the dirt road takes you close to the Tourões River, the living border with Spain. Follow shepherd's trails and farmland until you enter the Douro Internacional Natural Park, where, further north, the Tourões River joins the Águeda River, which, in turn, further north, joins the Douro River. The cliffs and horizons of the Douro Internacional are so imposing that some call it the Grand Canyon of Europe.