A Ponte Luiz I (Portuguese) is one of the six bridges which are most emblematic of the city of Porto and that crosses the borders of the city and Gaia where you can find the famous wine cellars of Porto. Its construction is based on a Belgian engineer project, the designer was a disciple of Eiffel, which explains its similarity to the Eiffel Tower. It has two floors, on the top line the Metro passes. There are walkways so you can enjoy the spectacular views of the Douro river with barges passing through the city. To access the Bridge D. Luis you can get there from the mall which has opened (rua Catarina), the funicular that goes right up to the bridge and enjoy the atmosphere of the resort and which offers beautiful views over this cosmopolitan city.
One of the bridges over the Duero, built to link Porto to the other side of the river. It's a National Monument, was designed by Gustave Eiffel, is made of iron and is very similar to Luis I bridge, but differs in that it has no lower footbridge. It took 22 months to build and was opened by King Ludwig I and his wife Maria Pia (hence its name) in 1877. It was the first bridge that allowed a rail connection between the banks of the Duero River. From the cruise ship you get a different perspective from the bottom.
This is one of the bridges that can be seen on the "Rabelo" cruise on the Douro river. It was designed by Edgar António de Mesquita Cardoso. It was constructed between 1957 and 1963, and for many years it held the world record for its 270 meter arch. It's built of reinforced concrete, 52 feet above the river. Traffic passes over the bridge.
This is one of the newer bridges in Oporto, built in 2003 over the Douro and designed by Adão da Fonseca, who achieved a world record for the constructive approach he adopted (the arc is 285 meters). The bridge is 371 meters long and the road has 4 lanes (2 in each direction). It's highly recommended to see it from below one of the cruises that depart from Pier Duero Ribera.
This is another one of Porto's famous bridges. I passed underneath it while on one of the Douro river boat cruises. The bridge was built very close to the Maris Pia Bridge, as a way to replace it for the rail traffic. Unlike the iron bridge designed by Eiffel, this one is built of white concrete, so there is a great visual contrast between the two. The most notable feature are the large pillars that come out of the riverbed to support it. This bridge was designed by Edgar Cardoso and opened in 1991 the day of San Juan (hence the name).