Barcelona travel guide - when to go, what to see, what it costs

Two nights covers the Sagrada Familia, one house on Passeig de Gracia and an evening walk, and that is genuinely all. The sights are spread across a big city rather than gathered in one old town, so the travel time between them is real in a way it is not in Krakow or Prague. Two nights means choosing three things and accepting you will not see the rest.

Four nights is the trip we would book. Day one for the Sagrada Familia and the Modernista buildings nearby, day two for Montjuic, day three for the old districts and the sea, day four for whatever you liked enough to go back to. That fourth day is what turns a checklist into a visit.

A week works only if you plan to leave the city with it. Montserrat, the mountain monastery an hour or so northwest by train, is a full day. Sitges down the coast is a half day. Girona is a day. Without one of those, a seventh night here is spent repeating yourself.

Barcelona has a mild winter, which is the fact most northern Europeans get wrong about it. January and February average highs of around 14 C and lows around 8 C. It rains but it does not freeze, and the outdoor tables never really come in. July and August average highs of 27 to 28 C with humid nights and lows above 22 C, and the sea reaches 24 to 25 C in August. May and October are the temperate months, with highs around 21 to 22 C. October is also the rainiest month of the year at roughly 75 mm.

For weather and crowds together, the best weeks are the second half of May and the first half of October: warm days, evenings you can sit outside in, and far fewer people at every ticketed sight than in summer. July and August are the months to avoid on crowding alone.

The fares run the other way, and this is the useful part. Our measurements into BCN put the floor from October through March: six months where the lowest fare we see barely moves, and the winter weeks are as cheap as any of them. August is the most expensive month by a wide margin, with the weeks either side of it the next worst. April through July sit between the two. So the cheapest time to fly here is also the coolest and the quietest, and October is the one month where low fares and good weather overlap. Our post on the cheapest month to fly south from Vilnius reads this exact route in more detail.

Several dates are worth planning around. La Merce, the city's main festival, runs from about 23 to 28 September around the feast day on the 24th: roughly 600 free events, human towers built by teams called castellers, the correfoc fire run, and the Piromusical fireworks at the foot of Montjuic. It has been an official city holiday since 1871 and is the best week of the year to be here if you do not mind crowds. Sant Jordi on 23 April turns La Rambla and Rambla de Catalunya into book and rose stalls; about 8 per cent of Catalonia's annual book sales happen that day. The night of 23 June is Sant Joan, with bonfires, fireworks and the whole city on the beach until dawn. The Festa Major de Gracia fills Gracia for eight days in mid-August, with residents competing to decorate their own streets, and it is the one good reason to be here in August. 11 September is the Diada, a regional public holiday, so expect closures and large demonstrations.

Josep Tarradellas Barcelona-El Prat, BCN, is 15 km southwest of the centre and has two terminals a long way apart. Which one you land at decides how you should travel in, so check it before you book.

The R2 Nord train is the fastest way in and runs from a station directly in front of Terminal 2B. It reaches Barcelona Sants in about 19 minutes and Passeig de Gracia in about 26, every half hour. Land at Terminal 1 and you first have to take the free shuttle bus 1.8 km to T2, which usually cancels the advantage. The Aerobus is the simplest option from either terminal: A1 serves T1, A2 serves T2, and both run 24 hours a day, 365 days a year, which makes it the answer for a flight landing at three in the morning. Metro L9 Sud has stations at both terminals and runs driverless every seven minutes or so to Zona Universitaria, where you change to L3. It is the slowest and it needs a separate airport ticket.

In the city you will use the metro; the twelve lines cover it well and a T-casual buys ten journeys. Inside a district, walk. Do not rent a car. It is useless here and parking is worse.

The most useful thing to know is that Catalan cooking is not Spanish cooking under another name, and the places that serve it are not the ones with photographs of paella outside. Start with pa amb tomaquet, bread rubbed with tomato and oil. Then look for escalivada, grilled and peeled peppers and aubergine; esqueixada, a cold salt cod salad with tomato and onion; botifarra amb mongetes, sausage with white beans, the plainest and best Catalan plate there is; suquet de peix, a fisherman's seafood casserole; and crema catalana to finish. Romesco, the almond and red pepper sauce from Valls, turns up next to anything grilled.

Two things are local to a season or a district. The bomba, a fried ball of potato stuffed with meat and served with hot sauce and allioli, belongs to Barceloneta. And between November and April, find a calcotada: charred spring onions eaten with your hands out of newspaper and dipped in romesco. It is the one seasonal Catalan meal worth planning a trip around and it does not exist in summer.

On where rather than what, markets are the reliable move: Santa Caterina and Sant Antoni both have bars inside and both are used by locals. La Boqueria is beautiful and now largely a tourist attraction. And move your clock: lunch runs from about two, dinner does not start until nine.

Barcelona is one of the busiest low-cost destinations in Europe and is reachable cheaply from a lot of places. Below is the lowest one-way we have measured into BCN from each origin we track, each figure showing the date we saw it. The month you choose moves this number far more than the day of the week does. If you want the other Spanish option from the same origins, our Malaga guide covers a city with a very different season.