Dom Luís I Bridge

It opened in 1886 and was designed by Théophile Seyrig, a former partner of Gustave Eiffel. Its 172-metre iron arch was the longest of its kind in the world when built, and it links Porto and Vila Nova de Gaia on two levels.

The upper deck carries metro line D and pedestrians, about 45 metres above the river; the lower one carries buses, taxis, bikes and pedestrians at the level of the Ribeira. Walking across the top is one of the city's must-dos.