The Dom Luís I Bridge, completed in 1886, connects Porto with Vila Nova de Gaia over the Douro River.
The double-deck metal arch bridge was designed by Théophile Seyrig, a former associate of Gustave Eiffel. Its lower deck carries road traffic, while the upper deck now carries Porto Metro trains and has pedestrian paths. The structure is about 172 metres long between its supports.
Construction began in 1881, and the bridge replaced the nearby Maria Pia Bridge as the principal rail crossing. Maria Pia, designed by Eiffel and completed in 1877, was later retired from railway service.
The Dom Luís I Bridge is often confused with Maria Pia because both are nineteenth-century metal arch bridges in Porto. Their silhouettes are similar, but Dom Luís I has two traffic decks and remains an active urban crossing.