They wanted to draw attention to their independence movement on La Diada, Catalonia’s national day, and they succeeded.
Hundreds of thousands of people draped in separatist banners and flags turned out in Barcelona and across the region.
Demonstrators formed a human chain – organisers said it stretched for 400 kilometres from the Pyrenees in the north to the border with Valencia in the south.
It linked up at exactly 17.14 in the afternoon, symbolising the year the Generalitat – an institution allowing Catalonia to run its own affairs – was abolished by the Spanish King Philip V.
The aim of the protest was to press the Spanish government to allow Catalonia to hold a referendum on independence.
Some opinion polls have suggested that more than 50 percent of Catalans back independence.
Although the region has significant self-governing powers, many believe it is treated unfairly over taxes and cultural matters – while the recession and spending cuts have aggravated rifts with Madrid.
A referendum is not permitted under the Spanish constitution and Spain’s Prime Minister Mariano Rajoy has pledged to block in the courts any attempt to hold one.