The Dom Luís I Bridge is a double-decked 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 of 172 m was the longest of its type in the world.
Théophile Seyrig had engineered the D. Maria Pia Bridge project nearby, whilst working as a partner of Gustave Eiffel. He now took sole responsibility for the new, major Luís I Bridge. The construction was begun in 1881 and the bridge opened on 31 October 1886 (the upper deck; the lower deck opened in 1887).
- Total length 385.25 m
- Weight 3045 tons
- The arch measures 172 m in length and 44.6 m in height