Barcelona resident and The Local journalist Esme Fox give us the lowdown on the city's La Mercè festival. Barcelona’s La Mercè is one of the biggest annual celebrations of the year and is held in honour of the Virgin of La Mercè, one of the city’s two patron saints. This year it’s being held from September 23rd to the 28th with the 24th being Día de la La Mercè. 'Castells' (human towers) are very common during La Mercè celebrations. AdvertisementMAC street theatreThe third element of La Mercè is the MAC Festival.