Why Travel to Barcelona?
The city has sensational architecture, led by the great and gaudy Gaudi, a lively, walkable centre, truly sensational restaurants and bars at reasonable prices, cultural activities by the ton and good beaches nearby.
Traffic and petty crime temper the pleasure of Spain's funkiest city, but only slightly.

Barcelona weather:
Due to its many urban attractions, mild winter climate and not over-hot summers, Barcelona tourism is possible all year round.
September and October are the wettest months but that's only rain in about one day in five.
Summer averages run from lows of 18C to average highs of 28C, and there are decent beaches within walking distance of the city centre!
Winter temperatures range from 5C to 14C .
All in all, anytime is OK but the very best time to visit would be the shoulder months of April-June for warmth, lowish rainfall and reduced tourist herds - aside from Easter holidays.

Things to Do:
Amazing Gaudi and 'modernista' structures like the Sagrada Familia, Casa Batllo, Casa Mila [La Pedrera] and Parc Guell make Barcelona an architectural fantasy land. Do pay to go inside Casa Batllo - which includes an English audio guide - that is totally fascinating and an astonishingly cohesive work of genius, and the Sagrada Familia if only for the extensive and informative museum and close-up views of the molten monstrosity. Parc Guell is free - more's the pity since it's usually over-crowded with school parties and tour groups.
There are other bizarre but functional monuments to Gaudi if time permits.

Then there's the busy and entertaining La Rambla pedestrian boulevard, aka Las Ramblas since it is actually a series of connected Rambla sections, with exceptional 'living statues' that actually have to audition before they're allowed to freeze there. Las Ramblas are also popular with petty, but clever thieves. More].
Tourists should keep their eyes open for not only mug-pockets, but also the colourful La Boqueria market on one side of La Rambla [the exquisite chocolates and fruit on offer are irresistible], another Gaudi sight just off the Rambla - Guell Palace in Carrer Nou de Rambla, and a favourite tourist relaxing and dining spot, the imposing Placa Reial.

Running along the east side of Las Ramblas are the narrow but lively streets of La Ciutat Vella [the Old Town] and the Barri Gtic [medieval area] including the stunning gothic La Seu cathedral and the Plaa de Sant Jaume [with weekly Catalan folk dances].

If all that old town claustrophobia or paranoia gets too much then head for the spacious, newish [1992] Barceloneta area at the south end of La Rambla, where the port, marina and beaches collide, providing good swimming facilities, sandy frolicking, seaside promenade walking, biking or skating and great, clean-air drinking and dining establishments.

The final just-about must-see in Barcelona is Montjuc hill for its great museums, city views, parks, gardens, 'Spanish Village', cable car ride and Magic Dancing Fountains.

Short Trips:
Sitges, 40km south, pretty seaside town and excellent beaches, favoured by gays.
Montsterrat, 40km NW, weird rock outcrops, caves and monastery.
Figueres, 90 min. north, for the fantastic Dali museum.
Tarragona, 90 min. south for Roman remains, medieval buildings, rocky views.
Girona, 80 min. north, pretty, mixed-up medieval river city.

Transport:
Barcelona is a large, complex city so if you are have just a couple of days it may be best to stick to the walkable central-south region from L'Eixample's Casa Mila down to the beaches of Barceloneta, with a couple of side trips to Sagrada Familia, Parc Guell and Montjuc using inexpensive taxis if necessary.
However, there is a useful Metro system for those with more time, though it's not exactly intuitive, including platforms where if you chose the wrong direction you have to exit the turnstiles [and pay again] to reach the other side. Get a day pass.
Bicycles? The city has bike rental stations in many locations so this could be a good way to get around if you have a credit card and feel adventurous, or private cycle rentals and tours are available too. Bikes can be delivered to your hotel.
Buses? Cheap but complicated routing and pick-pocket territory, so only for very savvy travellers.

Food: Superb Catalan and Spanish food is all over Barcelona. Try La Boqueria food market just off La Rambla, with its attendant restaurants every day except Sunday; Barceloneta [the port area] for seafood; Barri Gtic and the Old Town for little traditional eateries [though take care late at night] and Passeig de Gracia for larger, posher restaurants.
Don't forget that you can make a great meal just eating tapas snacks [especially good in Barri Gtic]. Spanish people eat dinner REALLY late. An 11pm start is not unusual in Barcelona.

Barcelona Festivals:
Feb/March pre-lent Carnival, [+ gay version in Sitges]
March-June, Guitar Festival
April, Contemporary Music Week
April/May, Ancient Music Festival
June, Dia de Sant Joan [dancing, music, fireworks]
end of June-August, Festival del Grec [theatre, music, dance]
August, Festa Major de Grcia [street music and events]
Sept, 4 days, Festes de la Merc, the city's biggest party, [parades, street music, human pyramids]
Oct -Dec, International Jazz Festival.

Barcelona Arts and Culture:
Museums and Galleries: A huge selection including: Museu Picasso [in beautiful medieval palace], Museu d'Art Contemporani, Centre de Cultura Contempornia [includes concerts & cinema], Museu d'Art de Catalunya, Fundaci Joan Mir, Museu Mars and plenty more.
Classical Music and Opera: Palau de la Msica Catalana[visually terrific too], Sal de Tinell [in Palau Reial, usually free], Sala Cultural Caja de Madrid. Also in many churches, and Festivals [see Festivals].
Theatre: mostly in Spanish, tho' Teatre Romea sometimes does English for foreign travellers.
Dance inc. Flamenco: Teatre Lliure, Las Sevillanas del Patio, Tarantos.
Live Rock and Jazz: lots on so check the weekly Gua dl Ocio or El Pais for listings.

Take Care: La Rambla is popular not only with tourists but also pickpockets, bag-snatchers and tyre-slashers, if you're unfortunate enough to drive there. Beware of 'distraction events' in particular. i.e. when some good/bad incident takes place that everyone looks at, except for the light-finger types who will be otherwise engaged in investigating your handbag, pocket or car seats.
The British Consulate says: '...be vigilant in Plaza Catalunya, La Rambla and surrounding streets of the Old City, Barri Gotic and be aware of the possibility of muggings in the Montjuic area. In the Rambla, Old Port [Port Vell] and Olympic Port areas thieves posing as police officers may ask to see wallets for identification purposes'.