The great D. Luis I Bridge is the symbol of Oporto. It was inaugurated in 1886. The engineer was a disciple of Eiffel.
There are two iron decks. The upper deck is the Metro track while the bottom deck is a traffic and pedestrian way.
To get to the bridge I used the funicular and then walked the lower deck to the Vila Nova de Gaia side of the river.
The views of the city and the area from the bridge are spectacular.
I recommend a trek to the bridge and over it to the Gaia area.