Fiesta de La Merçè - Festival of La Mercè (public holiday in Barcelona).
The 24th September is always a public holiday to celebrate La Merce, but the final dates for the actual Merce festival in 2008 have not been announced yet.
The city Festival of La Mercè span over a few days over the the weekend prior to the 24th September, which is usually the last day of the Merce festival and a public holiday.