Every April 23rd on the day of Sant Jordi, or St George, people in the wealthy northeastern region give each other a rose or a book in a celebration of love and culture.
Originally the tradition involved men giving their love a rose, while she in return would give him a book. But it has evolved and today women also receive books and flowers are given as well to mothers, daughters, friends and even co-workers.
The region celebrates a bank holiday to mark the day and throngs of people are expected to browse book and flower stands set up in the Catalan capital's historic centre as well as towns across the region.
Retailers expect to sell six million roses, and over 1.5 million books on the day just in Catalonia, which is home to 7.5 million people.
Catalan booksellers make between 5-8 percent of their annual sales on the day of Sant Jordi - which is also St George's Day in Britain - according to the Catalan booksellers association.
Musicians perform in the streets of Barcelona while authors sign copies of their books in booths set up for the day.
A man takes a picture of his girlfriend holding a rose and a book in the Ramblas in Barcelona. Photo: AFP
Catalonia adopted St George as its patron saint in the 15th century.
According to legend he saved a princess by killing a dragon with his spear while riding on a white horse. The dragon's blood caused a rosebush to grow and he offered one of its roses to the princess.
Since 1931 a book fair has been held in Barcelona on April 23rd - St George Day and the anniversary of the burial in 1616 of Spanish writer Miguel de Cervantes, the author of "Don Quixote".
Since then the tradition of offering books and roses in Catalonia on that date has thrived, even during the 1939-74 dictatorship of General Francisco Franco when the open sale of books in the Catalan language was banned.