Some 1.5 million people took part in Catalonia's annual independence rally in Barcelona on Saturday, the BBC reports, citing police.
Catalonia has a population of 7.6 million.
The size of the turnout for the rally, which is held annually on 11 September to mark the Siege of Barcelona 300 years ago, forced organisers to change its route.
Alfred Bosch, an MP from the Republican left of Catalonia, told the BBC: "All the flags I can see are the pro-independence flags of Catalonia with the lonely star right in the middle of the triangle.
"And everybody is wearing these flags. I have never seen so many pro-independence flags in my all life."