Porto, also known as Oporto in English, is the second largest city in Portugal, after Lisbon, and one of the major urban areas in Southern Europe.
Porto is my city and I would advise that visit.
It has great restaurants, beautiful landscapes, many monuments to visit and a great nightlife.
A product characteristic of Porto and is known throughout the world famous Port wine. Of course you can taste this nectar anywhere in the world, but surely that sitting on a terrace in `Ribeira do Porto` or `Cais de Gaia` will have another feeling. :)
*picture isn't mine*