It is probably no coincidence that the bridge passes more than a fleeting resemblance of its neighbouring bridge, the Dona Maria Pia bridge. Both bridges consist of huge and complex ironwork frameworks with a great arch supporting the transit way. This should come as no surprise as the D. Maria Pia bridge was designed by Gustave Eiffel of Paris tower fame! Opened in 1876 the D. Maria Pia bridge held the record for the largest span of any bridge of this type until work began on the Dom Luís bridge.
The names of the two bridges came from the then king of Portugal, Luís I, and his wife, Maria Pia of Savoy.

With a span of 172 metres (564 ft) and a height of 44.6 metres (146 ft) this was a great feat of engineering. The designer this time, Téophile Seyrig, had been Eiffel's partner on the previous project and showed himself to be a more than able engineer with this bridge.

One of the notable features of the Ponte Dom Luís I is it's two levels; one on top of the arch and the other suspended below it. Both decks were initially intended to carry road traffic but these days the top carries the Porto Metro trains as well as having a pedestrian walkway. It is worth making the crossing on the upper level, although being 60 metres (190 ft) above the waters of the Douro, it might not be for everyone!