La Mercè (Barcelona, Spain)

La Mercè transforms Barcelona's Gothic Quarter into a four-day fiesta with human towers, fire-breathing correfocs, and giant papier-mâché figures, offering over 600 free events. Attracting 1.2 million attendees—40% fewer than Notting Hill Carnival—it still leads in cultural density with 150 events per day, triple the average European street festival. The correfoc alone draws 200,000 spectators, a 20% increase since 2019.