This is a religious building destined to be the modern cathedral of Barcelona, identifying the city around the world. It was originally commissioned in 1882 by the Associació Espiritual de Devots de Sant Josep (Spiritual Association of Devotees of Saint Joseph) of the architect Francesc de Paula del Villar, who abandoned the project of the Neo-Gothic church because of disagreements with the promoters. In 1883, when only the crypt had been begun, the commission was handed over to Gaudí, who changed the old project and proposed a new one.

Gaudí conceived of the church with a basilical floor. Limited by the surface area of the land (on a block in Eixample, a Barcelona neighborhood), he took as much advantage of the space as possible, arranging the cloister around the temple. Its current state, in the process of being built, allows one to see the large size of the main nave, which will support high bell towers, the tallest of which will reach 170 m. This will symbolize Jesus, and around him will be four more, representing the evangelists. Over the apse, a sixth bell tower will be dedicated to the Virgin Mary. Currently, eight bell towers form a part of the facades of the Birth and the Passion, with four left to be built, along the main facade, dedicated to the Glory; all together, they will symbolize the twelve apostles.

The style of the temple is based on the Gothic style, from the development of geometric structures with quadric surfaces and the very ingenious application of decorative elements. The building draws together the essence of Gaudí’s building knowledge and experience. The structure with a paraboloid base, the generation of the columns of the central nave, and its tree-like shape that supports vaults with hyperbolic bases are features which stand out. Also remarkable are the interior modulation of the lateral windows that filter and spread the light.

To carry out the design of the project and its construction, Gaudí was aided by many collaborators, such as the architects Isidre Puig Boada, Francesc de Paula Quintana, Josep Francesc Ràfols, Joan Rubió, Domènec Sugrañes, and Francesc Berenguer.

On the northwest side of the building, Gaudí installed a workroom (an office for building direction, a study space, and a warehouse for materials) where he built models and experimented with geometry, colors, shapes, and sounds.

In 1936, the workroom was burned, and the majority of the plans were lost. Even so, the building of the temple was not stopped: the bell towers of the facade of the Birth were finished, and the building of the facade of the Passion was begun (1952-1978), the sculptural work of which has been carried out by Josep Maria Subirachs since 1986.
Listed in the Catalogue of the Architectural Heritage of Barcelona.