The dock of the banks of the River Douro, Porto is one of the most touristy places, with the famous Bridge of Luis I that was designed by the engineer Teofilo Seyrig. On the right bank is the old town that's been declared a heritage site, with the cathedral, the episcopal palace and the tower of the clergy, on the other side are the famous wine cellars of Vila Nova de Gaia and typical Porto boats carrying barrels. In this area there are plenty of restaurants and it's a lively shopping area in summer since is has the best view of the city.
As I said before, Póvoa is a traditional fishing village. I recommend leaving the tourist area for a while and exploring this typical fishing village. It is easily located just opposite the fishing port, behind the Church of Lapa. In these narrow streets you can see fishermen's houses, which are full of things from their trade (nets hanging on balconies, tiles with boats or the Virgin del Carmen). You will probably find fishermen mending their nets on the street, and small neighbourhood shops (greengrocers, fishmongers, etc.). The neighbourhood itself is ugly, but you have to look beyond its aesthetics.
One of the places not to be missed in Salzedas (apart from visiting its Monastery) , is a walk in the upper area of the old town, where the picturesque Jewish quarter is located. In the course of its steep, cobbled streets is a set of medieval houses built almost on top of each other (in some cases the balconies seem to touch each other) and connected by wooden walkways. Many of these houses are in ruins and require urgent intervention, but there are some recently refurbished, with brightly painted facades.
In the Middle Ages, Chaves was a walled town and the center of the city was protected by a defensive system of walls. Inside, people were staying in small houses and narrow multi-story granite and stone facades, taking advantage of the existing space. The streets were narrow, and to take advantage of the little amount of space they used usual construction of balconies on the upper floors, that go over the street. One of the most beautiful streets of this style is the Rua Direita, where you can see many of those balconies on both sides of the street that seem to touch each other, made of chestnut and pine. There are fewer balconies in the old town area.
The origins of Lamego date back to the twelfth century, with the construction of a castle on top of a hill (at nearly 550 meters altitude), surrounded by a walled enclosure with several doors. Today, it continues to maintain ancient dwellings in the citadel that's still inhabited. Of course, it's a treat to walk through the narrow, steep streets of this citadel known as "uptown", it's like you've been transported to the Middle Ages, with no stress or technology. Also, there are spectacular views of the "new" city or Barrio Bajo.