The Tagus River estuary in the greater Lisbon area is crossed by the substantial suspension bridge known as the Ponte 25 de Abril in Portugal. It was once named the Salazar Bridge since the Portuguese president António de Oliveira Salazar had officially commissioned it in 1960. However, following the Revolution of April 25, 1974, which brought democracy back to Portugal, it came to be recognised by its current name. The 25th of April Bridge is now regarded as one of Lisbon's primary images and symbols.

The steel building, which is intimidating in appearance, is almost 2 km long. The lower portion recently underwent renovation to make room for the railroad tracks. The 12 km Vasco da Gama Bridge, which spans the Tagus River from Montijo to Sacavém, north of Parque das Naçes, was built in 1998 and largely alleviated the bridge's notorious traffic congestion.

Over the Tagus River bridge, the sound of vehicles passing over metal grids can continually be heard. It is not suggested to drive too fast on the bridge since the grid on the deck renders vehicles unsafe or insufficiently stable at speeds exceeding 70 km/h.

A commission was established in 1953 by the Portuguese Ministry of Public Works to examine the technical and economical viability of constructing a bridge over the Tagus River close to Lisbon.

A public tender for building the bridge was announced on April 27, 1959. It was required to have two separate decks, one for transportation and the other for storage. As a result, the upper deck is designated for car traffic, while a lower deck is planned for train traffic.

Up to 14 different companies, 11 of which will be Portuguese, will be involved in the implementation of this task. There will also be days when up to 3,000 employees are employed to work on the bridge.

The engineering company Steinman, Boynton, Gronquist & London from New York won the bid.

After that, the government opted to put off connecting the rail link to the rest of the rail network and instead decided to merely open the vehicle-only platform to traffic.

The United States Steel International-led international consortium was given the construction contract by the State on May 9, 1962. Work on the bridge and associated road access started on November 5 of that year.

The Department "Gabinete del Puente over el ro Tajo" was established by the Ministry of Public Works to oversee all issues pertaining to the building of this undertaking (Office of the Bridge over the River Tagus). The National Civil Engineering Laboratory will also work with us to complete the project.

The platform for rail traffic has been built to accommodate two pairs of tracks with a space in between them in each direction. The removal of this division led to the entry into operation of a third pair of tracks on July 23, 1990. In 1998, a fourth set of tracks went into operation.

The operation of the bridge was given to a group of Portuguese, French, and English businesses known as Lusoponte in 1996. The Vasco do Gama Bridge will be constructed and operated by this consortium.

Spans on the bridge total 14. The middle span is unquestionably the most impressive of them all. It is 1013 metres long. It is 70 metres above the Tagus River's level. There are two piers that extend 190 metres above the river on either side of this span. These masts plunge 80 and 35 metres below this level, respectively, to the riverbed below.