Vila Nova de Gaia, across the River Douro from Porto, is famous for the production of Port wines. The traditional port lodges are still located in its center and most of them are open to visitors. While touring the lodges you can see (and smell) the barrels where the Port is kept, learn more about the making of Port and taste various different Port wines.
It is best to visit on a weekday and to stay away from the riverside where it is more busy and touristy. In the smaller streets away from the river you will find yourself going back in time and you will find Port lodges such as Offley, that offer tours and tastings but in a much more quiet, friendly and intimate setting.