I suggest 4 places to go, and a great place to stay
Pinhao, an interesting town on the Douro Valley
Casa de Mateus, this famous estate is near Vila Real
Quinta do Panascal, vineyard and port cellar , 12 minutes from Pinhao
Lamego, a beautiful church and spectacular gardens with its grand stairway
Stay at Casa Dos Barros Villa, Sabrosa not far from Pinhao
see the following posts for details.
Another way to explore is take a tour like this, Wine tours