One day in Porto is not enough
We were in Porto for only one day, and one day there is very little, it is better to plan two or three days in Porto, plus a couple more days in the suburbs.
We arrived there by train from Lisbon. Long-distance trains do not come to the central station of Sã o Bento (the one where the hall is decorated with azulejo paintings), but to the Campagna station on the outskirts of the city. And from Campania station to Sao Bento can be reached by train in about 10 minutes, and if you have a ticket for a long-distance train to or from Porto, you can not buy a train ticket. And the ticket to Porto even indicates the time of departure and arrival of the main train, and the departure time of the train between Campania station and Sao Bento. If you need to take the main train exactly on the one indicated on the ticket, then you can take any train on the train. And if you return back from Porto to Lisbon, it is better to leave Sao Bento at least 10-20 minutes earlier than indicated on the ticket, otherwise there is a risk of being late for the main train.
In general, we started our walk around Porto with a look at the paintings from the azulejos at the Sã o Bento station, followed by a beautiful view from the entrance to the station. And then you need to go a little to the right, and there will be Freedom Square, from where double-decker open buses depart. There are two routes in Porto - through the old city, and through the new one. If there is only one day, then it is better to take a route through the old city, and get out near the ocean, where the Douro River flows into it, and admire the waves there near the lighthouse.
And then take the bus again and get to Ribeira, have lunch in a restaurant on a narrow street that stretches along the river, take a walk along the old streets and climb to the second floor of the Luis I bridge, from where beautiful views of the city open up. If strength permits, it is better to climb up the stairs on foot, and not on the funicular, you can also see a lot of interesting things from the stairs.
It's also worth visiting Lello's bookstore, but we weren't so lucky - it was closed during a massive student holiday.
And you should definitely try the port wine. Only the wine that is made in the vicinity of Porto has the right to be called port wine, and it has nothing to do with the slurry that many remember from Soviet times. Real port wine is something fantastic.
And if there is time, you can still ride along the river on a steamboat or cable car near the Luis I bridge, but on the other side there is already another city - Villa nova de Gaia.