According to Christian tradition, Santa Eulàlia was a girl from Sarrià who, in the 4^th century, opposed the persecution of Christians at the order of the Roman emperor, Diocletian. Her faith led her to rebel against the consul, Dacian, who imprisoned her and punished her until she died. This 13 year old girl's attitude came to symbolise the defence of justice and equality, and her veneration by the people of Barcelona meant that in the 8^th century she became the patron saint of the city.

The festival is held on 12^th February, and around that day the Esbart Ciutat Comtal dance group stage a spectacle of music, song and dance entitled Eulàlia, in homage to the saint and to celebrate the values of freedom, solidarity and justice. The performance is based on a historical recreation of the life of the young girl, and includes her martyrdom, death and glorification.

The place the representation is held is also a homage to the saint: the main altar of the cathedral, just in front of the crypt holding her remains. A dozen actors represent Roman soldiers, and a dozen actresses witness the suffering of her martyrdom. They are accompanied by the figures of Dacian and Santa Eulàlia herself.