I’ve been to Barcelona twice and the second time I got to explore the sights more fully during the seven days I spent there (well, six, since I took one day to travel to Dalí’s museum in Figueres).
I said “couples” above, in the title. Barcelona is best experienced with a congenial travel partner, whether as a romantic couple or great friends. I went with a wonderful friend of mine, and had an amazing time discussing Picasso’s paintings and Dalí’s works, fruit on display at La Boquería food market, designs at Desigual clothing stores (Desigual is actually based in Barcelona), and the occasional Spanish flick late at night at a movie theater by the Mediterranean Sea.
Speaking of the Mediterranean, Barcelona is more than Gaudí’s houses and his Sagrada Família, or the other attractions I’m listing below. It is also a place with great beaches and great food. It's the city with the famous La Rambla, a street where you can see everything: street performers, many of them posing as statues, tourists of all kinds (a feast for any photographer), flowers and various kiosks, the food market La Boquería, which is a must-see sight in Barcelona, the Gran Teatre del Liceu, an opera house which looks amazing inside and out and where locals in very elegant dress flock on many a evening . . . and the list can go on.