The process for making port wine has several phases from the grape to the bottle.
First the grapes are collected in tall wicker baskets and transported to the wineries. This is a hard task because some vineyards are in a very hilly land.
Second, the grapes are tread in lagares, traditional stone tanks, or more commonly in steel and cement tanks.
Third, the grapes start the fermentation and at certain point brandy (grape spirit) is added to slow down fermentation. This way the wine gets sweeter from grape sugar.
Fourth, the wine matures in oak casks in the port lodges and finally is bottled for final maturing. This final step may have some variations depending on the type of wine.