The city of Oporto, Portugal lies at the mouth of the Douro river. In the green and steeply sloped valleys of this river the grapes for Port wine grow. Port is known as a fortified wine which means additional alcohol has been added to kill yeast and prematurely end the fermentation process.
Port wine owes its name to the Roman Empire. The settlement on the Douro river was called "Portus Cale" by the Roman armies who discovered it. Cale referred to the Celtic people who lived in the area.