The Luis I Bridge spans the Douro River and links Vila Nova de Gaia and Porto. It was established in 1886 and is a well-known landmark in the city.

The city of Porto had an increase in commerce in the second half of the 19th century. The eastern quarter, often known as the Brazilian quarter, was dotted with factories. The traffic to Lisbon and Vila Nova de Gaia was increasing, and the suspension bridge could not handle it all.

After rejecting a project by the firm Gustave Eiffel, which only called for a platform at the level of the riverbank with a drawbridge in the middle, the government decided to open a tender for the "construction of a metal bridge over the Douro river, in the place considered most convenient for the city of Porto, to replace the current suspension bridge" on February 11, 1879. Although it was a proposal that received a Grand Prize at the Universal Exhibition in Paris in 1878, it did not successfully connect the cities of Oporto and Gaia. Because of this, the competition required the creation of a bridge with two platforms as an essential requirement. The engineer Théophile Seyrig, who had previously designed and served as the project manager for the Dona Maria Pia Bridge, presented a number of proposals, and the Belgian business Société de Willebroeck was awarded the contract.

The Clérigos Tower and the Luis I Bridge are Oporto's two most iconic symbols.

Pontes para o futuro (literally, "bridges for the future") was the catchphrase used to advertise the 2001 celebration in which Porto and Rotterdam were named the cultural capitals of Europe. The city is connected by a sizable number of bridges on both sides of the Douro River in Portugal's second city.

The Ponte Dom Lus I, or "Dom Lus I Bridge," is the most well-known and renowned of all. Its structure is based on a design by German engineer Théophile Seyrig, who created the business Gustave Eiffel et Cie with famous engineer Gustave Eiffel. While working as the renowned French builder's partner, Seyrig created the Maria Pia Bridge in Porto, a masterpiece whose simplicity and cost astounded everyone who saw the competition for its prize.

There are two floors. The length of the top one is roughly 390 metres, while the length of the lower one is roughly 174 metres. The Porto Metro D line travels on the upper floor, while other vehicles like cars, buses, and trucks utilise the track below. People can go between the two floors thanks to footbridges.

The bridge's impressive feature is its substantial iron arch.

The bridge draws lots of travellers because of its fame and beauty. The Douro River and the neighbourhoods that have cropped up on both sides of the river can be seen from the upper deck's panoramic views, which are available to guests.