Fiestas de la Mercè, Fetsivals in Barcelona Las Fiestas de la Mercè take place between 22nd – 24th September and celebrate the patron saint of Barcelona. The actual day of Our Lady of Mercy is the 24th September, but the city hosts various open-air concerts over four days of festivities. More than 300 national and international performances take place in every corner of the city. You can also see firework displays, correfocs (fire runs), parades of gegants (giants) and capgrossos (big heads) and popular dances, such as la Sardana. Planning a trip to the Catalonian capital? Check out cheap flights to Barcelona, and read our Barcelona Guide for more general info on the city.