Port Wine is a natural and fortified wine,produced exclusively from grapes from the Douro Demarcated Region,in the North of Portugal about 100 km east of the city of Porto. São João da Pesqueira, Régua and Pinhão are the main production centers, but some of the best vineyards are in the easternmost area.
What makes port wine different from other wines, in addition to the unique climate, is the fact that the fermentation of the wine is not complete, being paraded at an early stage (two or three days after the start), by adding a neutral wine brandy (with about 77º alcohol). Thus port wine is a naturally sweet wine (given the natural sugar of grapes does not turn completely into alcohol)and stronger than the other wines (between 19 and 22º of alcohol).
Armando Vasques Osório Private Wine Cellar 1927