La Mercè is a festival that takes place in Barcelona every September, a tradition that dates back nearly 150 years. It started out as a festival to honour the patron saint of the archdiocese of Barcelona (Mare déu de Merce) – after she saved the city from a plague of locusts in the 17th century – and over time the festivities have begun to represent the popular culture of Catalonia. In addition, each year the festival invites another city to be its ‘guest city’, and this year it is the turn of Reykjavik, Iceland. What started as a government-led Catholic celebration ha s developed into a city-wide party, with events taking place over 4 nights in every corner of Barcelona. Make sure you clear your diaries for a weekend full of street parades, fountain shows, correfocs (fire-runs) and live music and dance performances at night. You should also make time to see Pyro-Musical – the firework show at the National Art Museum of Catalonia, the human towers, and the circus at Montjuic.