The Catalans have always been great seafarers, merchants and industrialists. Since they were united under the House of Barcelona, their nationhood has been threatened by marriages, alliances and conflicts with Madrid, and the road to their present status as a semi-autonomous region within Spain has been marked by times of power and wealth and troughs of weakness and despair.

Barcelona was not a natural site for human settlement. Its port was negligible and its heights, Montjuic, had no water. The oldest evidence of man in Catalonia comes rather from other sites scattered across the region, notably the dolmens of the Alt (high) Emporda and passage graves of the Baix (low) Emporda and Alt Urgell.

In the first millennium BC the lands around Barcelona were settled by the agrarian Laeitani, while other parts of Catalonia were simultaneously colonized by the Iberians. The latter were great builders in stone and remains of one of their settlements are still visible at Ullastret on the Costa Brava. Greek traders arrived on the coast around 550 BC, founding their first trading post at Empuries near Ullastret. It was the Carthaginians from New Carthage in southern Spain who put Barcelona on the map. They named the city after Hamil Barca, father of Hannibal who led his army of elephants from Catalonia over the Pyrenees and Alps to attack Rome.

In reprisal, the Romans arrived at Empuries and began the subjugation of the whole Iberian peninsula. They wiped out the Carthaginians as well as the Laeitani and established Tarraco in the south of Catalonia as the imperial capital of Tarraconensis, one of the three administrative regions of the peninsula.

Roman Barcelona can be seen in the city gate beside the cathedral, while the 3rd-century walls that once encircled the town lie by the medieval Royal Palace.

Foundations of the Roman city have been excavated in the basement of the Museu d'Historia de la Ciutat, and pillars from the Temple of Augustus can be glimpsed inside the Centre Excursionista de Catalunya behind the cathedral.

When the Roman empire collapsed, Visigoths based in Toulouse moved in to fill the vacuum. They had been vassals of Rome, practised Roman law, spoke a similar language and in 587 their Aryan king, Reccared, converted to the Christianity of Rome.