The Dom Luís I Bridge is a metal arch bridge that spans the Douro River between the cities of Porto and Vila Nova de Gaia in Portugal. At the time of construction its span was the longest of its type in the world.
The government held a competition for the construction of a metallic bridge over the Douro River on a site that was adjacent to an existing bridge that it would replace. Téophile Seyrig had engineered the D. Maria Pia Bridge project nearby, while working as a partner of Gustave Eiffel – designer of the Eiffel Tower in Paris. He now took sole responsibility for the new, major Luís I Bridge. The construction began in 1881 and the bridge opened in October of 1886. Today, it stands as an icon of the city.