Maria Pia Bridge
The railway line from Lisbon to Porto had to cross the Douro at a height of 61 metres above the river, whose great depth made it impossible to build an intermediate support and meant that the 160 metres of its width had to be crossed in a single span. Gustave Eiffel built a bridge with an arch of 42.50 metres of average spire and 160 metres of crescent-shaped chord. The bridge was erected entirely in cantilever fashion without intermediate scaffolding. The arches were supported during construction by steel cables that were attached to the upper deck. Each of the constructed sections served as a support for the construction of the following sections up to the central function, where the key that joined them together was installed.