Legend attributes the Carthaginian foundation of Barcino to Hamilcar Barca, father of Hannibal. About 15 BC, Romans redrew the town as a castrum (a Roman military camp) centred on the "Mons Taber", a little hill nearby the contemporary city hall (Plaça de Sant Jaume). The Roman Colonia Julia Augusta Faventia Paterna Barcino was outshone by the province's capital Tarragona but some important Roman remains are exposed under the Plaça del Rei, entrance by the city museum, Museu d'Història de la Ciutat and the typically Roman grid-planning is still visible today on the map of the historical centre, the Barri Gótic ("Gothic Quarter"). Some remaining fragments of the Roman walls have been incorporated in the cathedral butted up against them

The city was conquered by the Visigoths in the early 5th century, by the Moors in the early 8th century, reconquered from the emir in 801 by Charlemagne's son Louis who made Barcelona the seat of Carolingian "Spanish Marches" (Marca Hispanica), a buffer zone ruled by the Count of Barcelona. Barcelona was still a Christian frontier territory when it was sacked by Al-Mansur in 985.

The counts of Barcelona became increasingly independent and expanded their territory to include all of Catalonia, later formed the Crown of Aragon who conquered many overseas possessions, ruling the western Mediterranean Sea with outlying territories as far as Athens in the 13th century. The forging of a dynastic link between the Crown of Aragon and Castile marked the beginning of Barcelona's decline.

The city was devastated after the Catalonian Republic of 1640 - 1652, and again during the War of the Spanish Succession in 1714. King Philip V of Spain demolished half of the merchants' quarter (La Ribera) to build a military citadel, as a way of both punishing and controlling the rebel city. Official use of Catalan language was forbidden, and the University withdrew.

Barcelona and the province of Catalonia were annexed by the French Empire of Napoleon after he invaded Spain and put his brother Joseph on the Spanish throne. It was returned to Spain after Napoleon's downfall.

During the 19th century, Barcelona grew with the industrial revolution and the introduction of many new industries. During a period of weaker control by the Madrid authorities, the medieval walls were torn down and the citadel of La Ribera was converted into an urban park: the modern Parc de la Ciutadella, site of the 1888 "Universal Exposition" (World's Fair). The exposition also left behind the Arc de Triomf and the Museu de Zoologia (a building originally used during the fair as a cafe-restaurant). The fields that had surrounded the artificially constricted city became the Eixample ("extension"), a bustling modern city surrounding the old.

Famous people who have lived and worked in Barcelona include: Master Painters Pablo Picasso, Joan Miró, Salvador Dalí, Antoni Tàpies, Enrique Tábara, Eugenio Granell, Antonio Saura, Manolo Millares, Juan Villafuerte; Architect Antoni Gaudí.

The site of the cathedral was occupied by a basilica with three naves, destroyed by Almanzor in 925, remains of which are to be found in the subsoil and can be visited, and later by the Romanesque cathedral, begun in 1046 and consecrated in 1058. The present cathedral, begun in 1298, taking advantage of elements of the previous one, consists of three naves and an apse, covered with pointed arches. Most of the church as well as the cloister was built between 1365 and 1388, under the direction of Bernat Roca, the successor to Jacobus Fabre. Although the building was completed in mid-15C, the main facade was not built till the early years of 20C. Among the areas of interest, the most noteworthy are the Romanesque door of San Ivo (Sant Iu), in the older wing, in los Condes Street and the chapel of the Cristo de Lepanto, formerly the Sala Capitular, which is the outstanding part of the whole building, covered with a stellar vault.

Despite being named after its elegant Gothic buildings from the 13-15th century this area is actually much older, since Roman relics have been found here. From this period some parts of the Barcelona wall have survived (4 centuries), and can be see in main places. During the 19 century., les monuments the most seriously damaged monuments were the focus of an extremely careful restoration programme, which gave the quarter its elegant appearance.