This environment of conflict, especially the assassination of prime minister, Eduardo Dato, assassinated in Madrid by Catalan anarchists, led a military coup on September 13, 1923, by the captain general of Catalonia, Miguel Primo de Rivera, which was with the support of King Alfonso XIII. The new dictatorship abolished democratic institutions and began a fierce repression of trade unions. Mancomunitat suppressed (an institution founded in 1914 at the request of the Regionalist League, which had jurisdiction over certain administrative areas and cultural development), and banned the Catalan language and Catalan flag. Institutions were closed as the Orfeo Català, and even the FC Barcelona was suspended for six months.
The main event of this era was the 1929 International Exhibition, held on Montjuïc. For this event the entire urbanized area of the Plaza of Spain, and pavilions were built currently hosting Feria de Barcelona. The Exhibition was held from May 20, 1929 to January 15, 1930, on an area of 118 hectares, and at a cost of 130 million pesetas.32 addition to the fairgrounds, the show left many buildings and facilities, some of which have become emblems of the city, including the National Palace, the Magic Fountain, the Teatre Grec, the Spanish Village and the Olympic Stadium. Also built the Barcelona Metro, which opened originally in 1924 and expanded in 1926 with the Metro service between Bordeta Cross and Catalonia (now L1), linking the downtown with the site of exposure. Likewise, we built a funicular to get to the top of the mountain air and a shuttle to get to it from the Port of Barcelona (although it was inaugurated later in 1931).

As in 1888, the Exhibition of 1929 marked a major impact for the city of Barcelona at the urban, not only in the Montjuïc area, throughout the city were improving and upgrading works, is landscaped plazas Tetuan Urquinaona and Letamendi, they built the bridge of the Navy, became urbanized Plaza Catalunya, and continued the westward Diagonal and Gran Via de les Corts Catalanes southwest. Also made several public works improved the paving of streets and drainage, public toilets were installed and replaced the gas lighting for the company. Also, several buildings were remodeled, as the council or the Government, where the bridge was built across the street flamboyant Bisbe. It ended the Post Office and Station of France, who had several years under construction. It also built the Royal Palace of Pedralbes as the residence of the royal family. During that time it also built the first skyscraper in Barcelona, the Telefonica building on the corner Fontanella / Portal del Angel, the work of Francesc Nebot.
Finally, improved communication of the city, with construction in the 1920's El Prat Airport, the removal of level crossings within the city, improving links to the suburbs of the city, the burial Sarrià train (Ferrocarriles de la Generalitat de Catalunya) and the electrification of public trams. All these public works involves a strong demand for labor, causing a large increase in immigration to this city, from all parts of Spain. Also, the increase in population led to the construction of several working class neighborhoods of "affordable homes", as the Group Aunós in Montjuïc and Milans of the Bosch Group and Baró de Viver in kisses.