Free museums and free hours
The city gives away more culture than it seems: centers with permanent free entry, public museums with free afternoons and first Sundays without tickets across much of the network.
The always-free ones
Castles, civic centers and some public collections never charge: Montjuïc castle with its walls and several neighborhood interpretation centers sustain a whole Sunday without opening a wallet.
Afternoons and Sundays
Most public museums concentrate their free window on a weekday afternoon and the first Sunday of the month: arrive early, because free draws crowds. Check each museum's site; conditions change.
The right strategy
Combine free entries with a single big paid ticket per day: the real saving is not paying for two mid-size ones. And remember the cathedral, Roman streets and half the heritage city are already open-air museums.