Barcelona — how to plan the trip
Barcelona can be covered on foot and by tram, and still has a full-size beach inside the city limits. Three days cover the Sagrada Família, Park Güell and the Gothic Quarter; five let you add Montjuïc, Montserrat and one lazy day by the water.
Tickets to the Gaudí sites sell out weeks ahead and come with entry slots. That is the only thing you really have to plan before leaving — the rest of the city works spontaneously.
Food is a subject in itself: breakfast at the market, early tapas around 7 p.m., dinner after 9. The lunchtime menú del día is the cheapest way to eat well in a good restaurant.