The most popular options when visiting the Barcelona outskirts are: the Holy mountain of Montserrat and its sanctuary devoted to the black Madonna of Montserrat, patron of Catalonia; the Penedes region worldwide known for the wine and cava production (Spanish champagne); and the beautiful coastal town of Sitges.
One hour drive north it's worth a visit to Girona with the oldest and best preserved Jewish Quarter outside Israel in the world, and Figueras, home of the surrealistic Dali Museum.
