The power of the counts of Barcelona grew over time, and the territory under their jurisdiction expanded to include all of Catalonia. In 1137, Barcelona merged with the Aragonese Empire, forming the crown of Aragon. As a matter of fact, this kingdom captured many overseas territories and ruled the western Mediterranean Sea.

After the Muslim caliphate of Cordoba fell in the 12th Century, Catalonia became rich. In the 13th Century, its lands extended as far as Athens. This union survived until 1479, when the Crown of Aragon forged a dynastic link with the Crown of Castile. After that, Barcelona entered a period of decline. During the 14th Century, Barcelona ruled Malta, Valencia, Sicily, Sardinia, the French regions of Rousillon and Cerdagne, and some areas of Greece.

In the 15th Century, everything changed. Bank capitulation, the Plague and economic conflict with Genoa wrought havoc in Barcelona. The union between Aragon and Castile presented an additional problem. Sadly, the two kingdoms had no intentions to help the city – they were more interested in acquiring its riches. In 1462, the city rebelled against Queen Joan II. It was devastated by the siege which followed in1473. Castile took control of Barcelona, but even though it became part of the kingdom, the city did not benefit from the expeditions to the Americas, which helped Castile amass immense fortunes during the 16th Century.

Barcelona was devastated during the War of the Spanish Succession in 1714. Catalonia had sided with Austria and Britain against King Philip V of Spain. After the war, he remained the King of Spain and destroyed half of the tradesmen's quarter in order to build a citadel; to punish and control insurgents in Barcelona. Also, use of the Catalan language was officially outlawed and the city’s university was closed down.

In 1778, Catalonia was allowed to trade with America. Gradually, it regained its prestige and fortune. After Napoleon invaded Spain and proclaimed his brother Joseph the King of Spain, he annexed the province of Catalonia along with Barcelona. It wasn’t until after Napoleon’s fall that Barcelona was restored to Spain.