Why Catalonia has ambitions to break away
Catalonia was an independent region of the Iberian Peninsula - modern-day Spain and Portugal - with its own language, laws and customs.
In 1150, the marriage of Petronilia, Queen of Aragon, and Ramon Berenguer IV, Count of Barcelona, formed a dynasty leaving their son to inherit all territories concerning the region of Aragon and Catalonia.
This lasted until the reign of King Philip V. The War of the Spanish Succession ended with the defeat of Valencia in 1707, of Catalonia in 1714, and finally with the last of the islands in 1715 - resulting in the birth of modern-day Spain.
Subsequent kings tried to impose the Spanish language and laws on the region, but they abandoned their attempts in 1931 and restored the Generalitat (the national Catalan government).
General Francisco Franco, however, set out to destroy Catalan separatism and with his victory at the Battle of Ebro in 1938 he took control of the region, killing 3,500 people and forcing many more into exile.
The region was granted a degree of autonomy once more in 1977, when democracy returned to the country.
Calls for complete independence grew steadily until July 2010, when the Constitutional Court in Madrid overruled part of the 2006 autonomy statute, stating that there is no legal basis for recognising Catalonia as a nation within Spain.
The economic crisis in Spain has only served to magnify calls for Catalan independence - as the wealthy Barcelona region is seen as propping up the poorer rest of Spain.
How does the economy affect the issue?
The Catalan region has long been the industrial heartland of Spain - first for its maritime power and trade in goods such as textiles, but recently for finance, services and hi-tech companies. It is one of the wealthiest regions of Spain - it accounts for 19pc of Spain's GDP, equal with the Madrid region. Madrid, however, has a higher per capita GDP, as do the Basque Country and Navarre regions.
Secession would therefore cost Spain almost 20pc of its economic output, and trigger a row about how Catalonia would return €52.5bn of debt it owes to the country's central administration.
It would have a gross domestic product of €266bn, according to calculations by the OECD, which would make it the 34th largest economy in the world. That would make it bigger than Portugal or Hong Kong.
Its GDP per capita would be €30,000, which would make it wealthier than South Korea, Israel or Italy.
Catalonia's contribution to the Spanish economy is twice that of Scotland's to the UK.
Food and football
It's not just in politics, economics and language that Catalans see themselves as different.
They are deeply proud of their food and their chefs, such as Ferran Adriá, from El Bulli, and Jordi Cruz, who won his first Michelin star at the age of 25 - the youngest Spaniard to ever do so. El Celler de Can Roca was named the world's best restaurant for 2013, and is third this year. The footballing rivalry between Barcelona and Madrid is the stuff of legend - with 'El Clásico', played biannually between the two teams, a huge event for both cities.